Fretting over this is like complaining about little scratches on the inside of a new BBQ grill...of what consequence is it?
Your plate is
not used...notice there is no finish removed from the countersunk mounting holes from the previous installation of screws. The "marks" on your optic plate look the same as mine did....it's typical of small metal parts that get loaded into bins by the thousands and moved around after the manufacturing process, packaging, and final shipping.
I understand some people like to keep their firearms looking as if they never left the factory (me too, if at all possible), but the bottom line is...are you or anyone else going to be able to see either the top or the bottom of the optic plate
after it's installed with an optic? 'Not the greatest image, but the optic plate on my 5" Compact is hardly noticeable: