It's 64x64 but scaled to 640x640 (Unless i messed something up with the exported versions!), at least that's how I set it up in the godot project settings, not sure if that is true pixel perfect scaling but its set to integer and to keep the aspect ratio.
Ahh damn. I didn't notice that. I'm guessing its an artefact of the camera2d being able to move in subpixels or something. I'll need to figure that out before the next lowrezjam haha.