That is just a display issue for debug, HFR of 0 is never used in the mean calculation.
You might want to take a read through the post I made for this beta:
I added a temporary adjustment to allow users to set the size of the smallest viable star (in pixels). As you noted, this run is pretty data starved, but I was able to get it to perform quite a bit better by setting the minimum star size to a 6 pixel diameter.