Are you asking about the gain script?
It’s really a rather random thing to use.
I’d recommend installing graphs and just changing the gain every day manually.
GitHub - wiedehopf/graphs1090: Graphs for readsb / dump1090-fa / dump1090 (based on dump1090-tools by mutability)
A very good starting point is usually 5% messages >-3dB
awk "$(cat /run/dump1090*/stats.json| grep total | sed 's/.*accepted":\[\([0-9]*\).*strong_signals":\([0-9]*\).*/BEGIN {printf "\\nPercentage of strong messages: %.3f \\n" , \2 * 100 \/ \1}/')"
After that any changes to reception are most likely only noticeable over multiple days or comparing to a second station.
Also see this thread where the above command is explained a bit:
Thoughts on optimizing gain - #2 by wiedehopf