This seems to be the right place for my FAP question:
I have a FAP28 (actually my best one...

) and I used it to heal fast while hunting. Later I checked out my FAP18 and was wondering that it heals up to 26 Health whereas the FAP28 only heals 20 Points max. I don´t get it, where is the internal logic? What do those numbers (5,10,15,18,28) really mean?
BTW: My experience is that I skill much better with the FAP18 compared to FAP5.