Have no idea, but the numbers on the breakers are the max ratings, not necessarily what the circuit is actually carrying. Thus one is up to 24v and up to 25A, while the other is max 12v and max 15A. Are there also 12v fuses somewhere? Breakers are often used where occasional overloads can easily occur, e.g. for the slide-out motors, hydraulic levelers, etc. Could also be the feeder line for a 12v distribution panel elsewhere, one that has smaller fuses and multiple branch circuits.