I’m trying to use asterisk/ztmonitor as a ‘level monitor’ for certain calls.

I’ve checked the docs and the source, but can’t seem to find the units and the max/min on the graph for ztmonitor (i.e. -30 to 0 db, 1 db steps, etc). Does anybody know what they are? I’m hoping I can use this to apply appropriate padding, but need to know how hot the signal is.