I will try again a few times today using y'all suggestions.
will update later with results.
put him in a big cup and tried again.
got 5 consecutive reading between 184g and 187g
so now i’m going to say that’s probably about where he is.
he looks healthy and growing.
but he was severely underfed by the pet store (and by me before i properly educated myself).
hopefully i didn’t stunt his growth too much and he can end up being as big as he can!