Grinding might mess with structural integrity. I would compare with others of the same design...
Does that say "22 ton"? Dang what are you jacking?
My guess is that it's a manufacturing defect where the sand cast wasn't formed properly. I think they should look like the picture below. I'd probably just grind it out and remove the excess metal that shouldn't be there. Unless it's easier to return them for a new set.
It might mess with the structural integrity, but a little off the top doesn't look like it would be too big of a deal.
I'll be using these jack stands on my 4Runner. I got them for the structural integrity and security of the huge pin. The pic in the post below yours actually shows the type of jack stands I bought.