BPC/Invention question

Playing with some BPC’s I recovered from a wreck, and I don’t understand the wizardry of how industrial skills work with them.
If I have a Condor BPC and say I want to Invent a Raptor BPC, why do the Success Probability Modifiers not add up?
The Blueprint modifier is 30%, Decryptor is 80%, Skills and Implants is 27.5%, and yet my probability of success on any run is only 68.9.

Percents are not all added together. They are ultimately multiplied.


My advice is just try it. Datacores and decryptors are cheap. You may not be successful, but you learn something.