I’m not sure what you want me to do, You are welcome to return it, no problem. The specs match from what I can see, all soldered components have a tolerance and will always vary much more so in through hole mounts. The holes match on the board and the ramps.
If it’s just a case that doesn’t fit, what one is it?
Did you get your mega from arduino? The bottom will be white if it is.
Again, what would you like me to do?