It would not be 60A as the short stop series maxes out at 50A. 6A is an odd size but I've seen one on my motorhome and ended up replacing it with a 5A fuse. I think it goes to the memory backup power for the radio but I am not sure.
If this is perchance for a Coachmen RV and it has a little bus bar and plastic holder arrangement for up to four of these breakers, I'd suggest replacing the plastic holder with the equivalent metal bracket that wiring products sells. The reason is that the plastic holder insulates one of the lead wires from the base of the terminal stud on the breaker, forcing the current to flow through the nut and the threaded interface between it and the stud. The threaded junction is not designed to be a current carrying connection. (The metal brackets have the same spacing ad the plastic holder so the little bus bar piece will still work.)