Yeah, it's not an issue--it's just standard paper wrapping for a double-sided board. When you print a board on two sides, you're actually printing paper that is glued to the cardboard. One side has to wrap over the other a little bit. I chose for the bigger side of the board to wrap onto the standard side to provide seamless hexes when the bigger side is combined with the board extension.
This REALLY makes a difference when playing with the extended board. I had this setup for a game when some friends came over. They didn't realize it was actually two different boards at first.