In the attack screen, player is informed with how much xp he/she will get from an attack. If xp gain from that base is below xp cap of the player, he/she should destroy the base 100 percent in order to gain max xp. But this is not obvious for xp capped bases. You can gain max xp even if you destroy 11 percent of a base.
So, can you add information for xp capped bases, what percent is needed to gain max xp. You can say attack and learn, this is what i am doing now, but it can be improved with extra percent information for max xp for that base in attack screen details.