This error doesn't affect operation. I have a P10 matrix on a BeagleBone Black which I setup on a NULL controller with id of 10000 which becomes the start channel. There are 6144 nodes so 18432 channels. That makes the last channel 28431. When I use the check sequence tool it reports:
Models spanning controllers
ERR: Model 'Matrix' starts on controller 'Matrix' but ends at channel 28431 which is not on a controller.
The Beagle Bone in remote doesn't care and dutifully displays the show
