So, to make sure I understand:
You spend 15,000 on a Obvious Cyberarm (capacity of 15). This starts at 2 STR/2 AGI.
The attribute increase item on the mod chart shows Rating: Rating, Capacity: Rating, and Cost: Rating x 5,000 if I remember correctly.
So if my STR is 6 and I want a punch (or using a weapon in that hand?) to be 8 STR, I would then make the attribute rating 6, making the capacity 6, making the cost 6 x 5,000? But I would still use by base 6 STR for anything else involving a STR check unless it was specifically related to my arm.
So is that count as 6/15 capacity on the arm? The other 9 I could use for AGI or armor other components I assume.