When set to a non-zero value, the overworld loading routine is overridden by loading a level value stored here, minus #$24 if it's above #$24. For example, the intro level (level C5) is loaded this way by storing #$E9 to this address.
Depending on whether the player is on the main overworld or a submap, the level in question is either in the 0xx or 1xx area.
