When using truck brakes and therefore trailer brakes get applied you are NOT sending FULL battery voltage to trailer brakes ----proportional braking based on how hard truck brakes are applied
IF you are going 20 mph and apply trailer brakes via MANUAL Lever FULL battery voltage WILL be applied to trailer brakes and you MAY or may not full lock up trailer brakes.
S/B able on dirt/gravel....maybe on asphalt---maybe BUT should notice strong braking action
Setting on 10 is too high in my opinion----brakes are still too loose.
Spin wheel and it should rotate 3/4 turn then stop when brakes are adjusted.