Why does Sunlu S4 say 21% when meter says 10%?

Yeah, thats the problem 10% is the low range on those cheap RH, and apparantly what they go to when they fail or cant sense humidity.

So like right now, both of them say 70.4F at 10% RH.

If i breath on them, they instantly jump up to 30-35% RH (and 70.6F).

So they are sensing something, but completely worthless