7-wire trailer plug question

I installed a trailer brake controller in my XJ and I purchased a kit for wiring the the 7-wire plug. The kit came with the wiring, plug, breakers, etc. The instructions say the 12v hot lead from the + batt cable to the rear should run through a 40 amp breaker. However, this is 10 gauge wire I'm using, which is rated for 30 amps max. Aren't these instructions wrong? Shouldn't I be running this through a 30 amp breaker?

Thanks for any help.

I've noticed that with a lot of automotive installations the wire is under-sized compared to what you would install in a home. I always err on the side of caution. I would either upgrade the wire or downgrade the breaker/fuse.

When installed the 7-wire plug on my XJ and 4-Runner (I didn't use a kit) I ran 12 gauge wire and put it on a 20amp fuse and haven't had any problems with either installation. I've towed 2 different campers with the XJ and 3 with the 4-Runner. All had brakes and charged the battery from the tow vehicle.