Question about the parameter action thr=0.002 in ava metric.py

[Condor-G]

Hello everyone, Sorry to bother you.
I am experimenting with the dataset of AVA type. I find that in the file named mmaction\evaluation\metrics\ava_metric.py, existing the code action_thr: float = 0.002, which seems to affect the final AP result. So why should the parameter action_thr be set to 0.002, not 0.5 or 0 or whatever?
My personal thinking is that in multi-label behavior recognition, 0.002 might allow for the capture of as many behavior labels as possible, but why not 0.5? After all, 0.002 is too small. I am not sure whether this idea is correct. Please help me.
Thank you!!