In my current game as the US, I had an unusual result in a recent combat. A tiny band of 50 Indians were attacked and destroyed by my troops, but part of the combat report stated that 200 prisoners had been captured in the fight.
What is going on here? It seems odd that prisoner reporting would be subject to fog of war, since they are supposedly in your custody, so you should know how many people you captured.
Prisoners just seems based on the initial size of the element in question rather than its actual strength. I guess you could rationalize it as the number just being the number captured in all of the run ins with that element combined.