When I apply a pattern with the render option or the bucketfill it doesn't completely fill the selection without being off center/ having a offset (I'm not good with GIMP terminology ☹️)
I DID NOT apply a pattern on a separate layer
I circled the parts of the pattern that are "off center"
edit: I decided that the easiest choice for fixing this was to erase the offset (which are apparently called "seams"), and then stretch the remaining tiles to fit the selection, and it looks pretty much like how I wanted it to look