Prints coming out smaller.

Im not exactly sure how to ask for help with this problem, but I have an Elegoo Neptune 4 plus, I use Cura as my slicing, my Machine Settings have my bed plate at 330mm x 330mm x 387mm, Elegoo has the bedplate size listed as 330mm x 330mm x 387mm, and I have even measured it myself and got the same measurements, yet when I sliced a print with exact measurements, the print itself came out about an inch smaller on all axes. Am I doing something wrong? What can I do to fix this?