
When playing Cabinet Retreat, Governor Council, Wargames, or that one for all characters, the additional XP is all dumped into the next stat increase.
This is especially noticeable when using multiple Cabinet Retreats or so in a single turn. I'm not entirely sure how exactly the additional XP is used in comparison to "normal" XP earned every turn (I haven't seen large amounts of XP lost due to a failed roll, and additional levels are learned). However, I would expect the additional XP to be used to increase various stats, instead of only the one.
