The size of the mark doesn't matter because we know from the testimony that Lovelady's arrow was drawn mostly in the black.
So, what we have doesn't have to look like an arrow. It only has to look like a mark that somebody made. And it does.
And keep in mind that we know for absolute certain that another arrow was drawn, and this is the only other mark on the photo, and it looks discreet. It looks distinct. It looks neat and tidy. It looks quite sharp. In no way does it look like a scratch or a smudge or the rendering of dirt. An honest broker would at the very least honor the possibility of it. Why reject it outright? Is the idea that Lovelady disguised his arrow as part of Frazier's to make two arrows appear as one really more plausible? Behaviorally? No one would behave like that, and no one did.