So I have tried a few different times in a few different ways and 2 different versions.

I tried on an older version on this on 1.18.1 but it didn't work so I tried the newest version and it seems to do the same thing, it isn't pasting the schematic under 0

for extra info I am pasting a large project that has a lot of things underground I am pasting it in a flat world and would prefer to keep it the same level but it doesn't seem to be something I can fix on my own.

Edit: I figured it out, I needed to turn replace blocks on, I hadn't done that