Check the battle logs (if you have the option of logging the battles on). It was kind of illuminating to actually realize that valour is tracked on soldier level, not just as a value inherent to the unit. So on valour 1 unit you might have a lot of valour 0 soldiers, some with 1, some with 2, and perhaps several with higher numbers. Just guessing here - the one number shown in the game is average of these,

It´s also interesting to see the kills divided to lone soldiers. Always fun to see that your king racked some 3/4 of units kills.

-Juha