( Bug or Design with cropping?

I noticed that when I have the resolution set for 704 x 396, and I use cropping, there are only certain instances where pixels are dropped by cropping.

For instance, if I cut the top off by 2 pixels then it becomes 704x394. Same for the bottom.

However, when I shave 2 off of the side, it is still listed at 704x396. But when I shave 2 off from both sides, there is only a difference in 2 pixels total (instead of 4) reading 704x398.

I realize that the reason the height went higher (398) instead of lower in this instance is because the image is probably stretched in all directions to keep it at a width of 704 but why is there only a difference in 2 pixels instead of 4? By this logic, shouldn’t shaving off 4 pixels result in a resolution of 704x400?