Toughness increases over it's potential
Toughness went from 24 to 25 while it's potential was 24 (and remained so).
Character is a human fighter. I'm not wearing any toughness enhancing stuff (although I have some in my backpack). My potential max is 24 toughness and 20 willpower (and I have them both maxed) and 21 dexterity (I have 20). I ate ~15 morgias trying to up it further and also used ~20 mosses of mareillon. I gain the +1 dext quite soon and while battling Steel Golems I levelup and I notice my dexterity potential going to 22 (yay!). After having killed all Golems I notice I'm finally L+ and decide to pray for crowning: got =Fire and Grod (yay!). At this point I notice I have 25 toughness and check my stats: it's potential shows to be 24. It doesn't change while walking around etc..