to hit %?

[Suicide Junkie]

Base + positive modifiers - negative modifiers.
<1 is treated as 1%, and >99 is treated as 99%
The SE4 Talisman forces accuracy to be 100% always at this point.

Unfortunately this means that if you have a 10% chance to hit, and add a sensor worth +10, it doubles your hit rate.

Therefore when modding, be sure to keep all your modifiers small, so that you do not stray too far from 50%. Thus ensuring that your modifiers continue to provide sane effect amounts in practice.