Bob Engelhardt writes:

With the wrench set to 20 ft-lbs, it clicked at a torque of 17.4 ft-lbs.
13% low. Set at 50 ft-lbs, it clicked at 43, 14% low. HF claims
that it's accurate to 4%.

If the error was repeatable, you could write your own calibration chart.
But as you observe it isn't repeatable.

Why do imagine you in the HF store with your lever and coffee can, going
through every torque wrench on the shelf to find a "good" one?