Ply gem replacing sash window glass
Successfully disassembling sash windows, replacing the glass, and reassembling can be complicated and difficult. If the replacement glass pane is oversized at all, you will not be able to screw the sash frame back together and will likely crack the glass trying. If slightly undersized, it might work. If it is at all thicker, it likely will not fit in the rubber surround that the window is equipped with.

Assuming you measured the original glass properly, I would return the replacement pane you bought and insist on the proper (original) size.