For most linear brakes, set Motor Min and Batt min to the same value (e.g. -40A). Batt Min is more relevant at higher speeds while Motor Min becomes more dominant at lower speeds.
In your case: At full speed you only get 20A of braking power, while at lower speeds braking goes up to around 30+A and close to stand still to around 50A.
Read more here: Optimum Vesc settings? - #41 by Trampa