As long as they all end up at the same height, all is good.
What you want is a flat plane for the mb. The screw holes may or may not be at the same altitude across the case. Hence the different length standoffs.
Or, they put some wrong ones in there.
Once they are all installed, are they at the same height? If yes, proceed. If no, get some different ones.
No, the two longer ones are higher up than the rest they gave me. I will just remove them and put in the spares they gave me that are all the same size