sher
Baron
More troops will be in a batch more will get promotion. Exact mechanics is irrelevant actually. Provide more trainers and more troops in a batch to get more upgrades. Kinda stupid and not correlates with skill description but that how it works. Possibly quantity of troops in a batch get multiplied by cumulative XP from trainers and then divided by XP needed for single upgrade to get number of soldiers to upgrade - all behind the scenes, no numbers, no nothing.