I had this situation where there was a stack of units with a strength value of X. I attack them and kill them all. After the battle, there is another stack of units with a different combat strength on the same tile I attacked.

From what I understand, they only showed and calculated the strength of the 12 first unit and hide the rest of the unit under the stack. There should be some sort of information on the screen that shows that there is another stack under it with it's combat value. Or really limit the size of a stack to 12 units on a world map square.

I have taken some screen shot to illustrate the problem if you need them.