Axle rating is not the sum of the whole.
Axle is rated for 6K Total
Wheel is rated for 3200 each (6400 total)
Tire is rated for 3520 each (7040 total)
3100 on one wheel position is not overloading the axle rating provided opposite side wheel position is not over 2900 for 6000 total.
Rarely will you find same weight being carried by each wheel on a trailer axle due to components and/or storage above that wheel position.
Rarely are folks even aware of the differences between wheel position cause they don't get individual wheel weight..just combined axle weights