"NEIKO 20743A 3/4-inch Drive Digital Torque Adapter, 150-750 Foot-Pound"

That's cool.

I looked for a user guide on-line, but couldn't find one.

It looks like there's a black button on the back?  Is it a button?  Or
what's that for?

https://m.media-amazon.com/images/I/61+Gn4Y2XSL._AC_SL1300_.jpg

I've never had my traditional torque wrench calibrated, but I've heard
my Airframe & Powerplant licensed friends must periodically.  Is there a
way to adjust the digital adapter's calibration?