I used the Brinkmann temp gauge on my first build and wound up taking the thing back to HD. I used the boiling water technique and got it to read 212 by adjusting the back nut. Put it back in the UDS and was 50 degrees low at 350 on the Maverick. I would suggest taking it back and looking for another brand name or buying a decent one on Amazon or somewhere.
The early bird may get the worm, but the second mouse gets the cheese.