I have a copy of Staun's that cost about $20.00.
I find them impossible to adjust accurately. Some go down fast, others slow and where they stop, nobody knows.
They were all set to what I thought was 18 psi, only to come back and find one tyre went down to 10 psi and still may not have finished.
Now I put all 4 on and when the sound of outgoing air slows down, I check with a gauge & let the remainder out manually.
Maybe mine were exceptionally poor quality?