I think you're confusing slots with switches. Slots in that instance are performance slots, of which there are 5 per Performance, and therefore 5 dedicated switches on the Remote. However, there are 4 FX switches on the Remote that can be assigned to any of the 8 FX slots on the KPA, up to four per switch. Each Performance slot can have it's own combination of FX assignments for the 4 FX switches, so in the above instance, Performance slot 1 has a switch that's assigned to FX A On *or* B On, whereas Performance slot 2 has a switch that's assigned to A and B On *or* A and B Off...
Edit : this reply is for @Hurricane!
Cheers,
Sam