Not calculated, but yes. There's no calculations involving skills, so you're fine to just put a number and (changed number) in the blank so that you don't have to worry about it. That said, there are calculations for modified attributes, which was part of the getting ready for some future stuff. I haven't yet hooked the modified attributes in, though, which is something that I need to go back and remember to do.
You're able to set the modifiers by hand, there's also a special field for calculated ones thanks to armor add-ons or the like, which is handled by the sheet itself.