Tilemap Boundaries not fitting the Tilemap

Hey there, I'm currently using a Tilemap to create a game world in a 2D Game. Now that I'm restricting the movement of the camera to the bounds of the tilemap, which is working fine at least for the right side of the tilemap.

For some reason, the boundarie of the tilemap arenot fitting the borders of the tilemap, which results in the camera be able to be moved to far (exept the right border)

In the Editor, the boundary of the tilemap looks like this when I select the Tilemap:

Is the anything I can to to make these boundaries fit my tilemap? Trying to "fill" the Gap only resulted in the boundaries keeping their distance to the tilemap :(