How'd I get these big ID numbers?

I was just using the auto terrain thing and these numbers showed up instead of the ID when I exported it

Those tiles are flipped/rotated - the highest four bits are the flip/rotation flags, and when they’re set, the full GID gets large.

Just an additional note for completeness. The Terrain Brush will by default not flip or rotate your tiles, unless you have set one or more of the following flags on the tileset, which control whether the terrain tool is allowed to transform tiles (either for randomness or to make the set complete):


On Discord, it turned out they had Flip Vertically enabled for some reason.