In the following battle log, you will see that the Union army is said to include 2x light artillery (6 pounders), 2x 10 pounders and 1x 12 pounder artillery.
So far so good, except that I happen to know I have no 6 pounders in that force. And when I check after that battle, one of the divisions engaged has 2x 12 pounders and 1x 10 pounder, the other one each of 10 and 12 pounder.
So it looks to me like in the battle screen, two of my 12 pounders have been converted to six pounders.
Is this normal? Is the game representing something else (like disadvantageous ground)? Or is this simply a bug, either in the battle screen, or in-game?