I've seen that are you are making several posts around this topic so perhaps I can dig a bit deeper here to give you (and others that might be wondering the same thing) a better understanding of this negative quality.
Think having the SINner quality as if you are living a double life.
On the one hand you are Bruce Wayne. Bruce grew up in a Mega. Your father were also born within the corp and you never met your mother, but you have been told that she was very special - just like you. Most aspects of your life were handled by the corp. Your life was the Mega. Because of your natural talent with anything matrix related perhaps you were groomed to take over the matrix security corner office in Gotham City one day. Everyone knew who you were. Then something happen. Maybe you got blamed for something terrible that someone else did. Maybe this involved your father getting killed. Maybe not. You were pushed out in the shadows. Forgotten. For now.
You still have your trust found that your father set up in your name (in Bruce Wayne's name), but the trust found is being maintained by Alfred, a trustee. An old friend of your fathers and now one of your contacts. What this means is that Bruce Wayne's Middle Lifestyle is being payed by this trustee and each month there is about 500 nuyen of pocket money that you get to spend on other things. Just enough to live.
But living is boring. So... on the other hand you have now been taken up shadowrunning. In the matrix you are using a persona icon in the shape of a black bat and on the streets you are not known as Bruce Wayne, instead you are getting known as Batman. You have a natural gift of slicing through IC. You don't even need to use a cyberdeck. Your skills in the matrix are stuff legends are made of. If your enemies would ever find out that you are Bruce Wayne then things might go bad. If your new friends finds out, then things will go even worse.
One of the first things you did when being kicked out of the Mega was to get a false ID. Someone named 'Dick Grayson'. You didn't get to pick the name. It's not really a perfect match. Dick is 12 years younger than your real age - so you try not to use it too much, but it seem to work in situations when you don't want to leave a paper trail back to Bruce Wayne. Dick even have his own apartment and a fake firearms licence. This is your Shadowrun alter ego when you you need to have a SIN for whatever reason while working as Batman and you don't want to incriminate your real Bruce Wayne identity.
You still believe in the Mega. You still pay taxes to the Mega. You walk and talk as if you were born within the Mega, which is not strange since you spend your first 23 years within the Mega and never even sat your foot in the barrens until just a few years ago. You will probably defend the Mega in discussions, but you are trying hard to keep a low profile and not draw attention. You probably still have a few loyal contacts within the Mega and you are probably also very reluctant taking jobs that directly involve that Mega. And were you to set foot in the Mega you are confident that some facial recognition will spot you and the speaker might say something along the line with: "Welcome back Bruce Wayne, it has been 892 days since your last visit. Unfortunately your access is still revoked. Please remain in the lobby. Security will shortly escort you out of the building. Thank you for your cooperation. Have a nice day, Mr Wayne". Or at least that might be what your character think will happen if he ever set his foot inside the Mega again.
Your biggest fear is that one day someone from your old life might come knocking on your door. The Mega also have your real biometrics on file. Because of all this you try to keep a very low profile and you are also rather paranoid. You don't leave fingerprints or blood samples around. You routinely hack surveillance cameras and erase yourself in real time as you pass them. You have even thought about trying to get the whole Bruce Wayne identity 'Erased' which mean you would become a SINless like most of the shadowrunners you run with, but to do that you need to save up a lot of money (and karma, this might even be one of the short term goal motivations why you are running). You would probably also need to give up your trust found and the apartment Bruce Wayne is living in. Not ready for this yet. Maybe next year. Must save up more nuyen. Maybe 10 more runs.
Having a corporate SIN negative quality give you 25 karma during chargen, which is huge. It is supposed to have a rather big impact on your character and how you play it. Other negative qualities that also give you 25 karma (and are also supposed to give a similar impact on how you play your character) include, but are not limited to; Extreme Allergy to Sunlight and Burn-Out level addiction.
Hopes this helps.
For inspiration; The character Alex Kamal (the fighter pilot from Mars) in the sci-fi TV-series The Expanse does a pretty good portraying how a corporate SIN negative quality might be played out and some of the situations that might arise when you are used to belong to, what your new friends considers to be, 'the bad guys'.
