If you compare this side to the other side of the hoof, you will probably see that both grooves are the same depth, only the side you're worried about has a flap of extra frog hanging over it. It looks weird because the shoe doesn't end at the heel on that side. I'm not sure if there is a practical reason for this shoe to be on crooked, but maybe ask your farrier next time they are out. You can see that the shoe ends at the buttress of the heel on the left side, but curves beyond on the right.
The flap of frog is nothing to worry about but as I said, you can get your farrier to trim it off next trim.