How to adjuste _std_weight_position and std_weight_velocity

[WGY907]

I tried to change the values at random ,The evaluation indicators at MOT16 have changed . The author mentions it in the code “Motion and observation uncertainty are chosen relative to the current state estimate. These weights control the amount of uncertainty in the model. This is a bit hacky.” I want to know How do you get an exact value for a std_weight_position and std_weight_velocity. Thanks!