Portable ESD Testers Resistance Ranges (pass/Fail)

While looking at the device manual of a 498 Portable ESD Checker, I have seen a range of resistances that equates to a Low Fail, High Fail and Pass.

900MOhms < R = High Fail
800KOhms < R < 900MOhms = Pass
R < 800KOhms = Low Fail

What is the basis of these ranges? What happens if the person is low fail? What happens if the person is high fail? Thank you.

For the resistance range, the low fail can be considered a safety issues. From and ESD control point of view, there lower limit does not matter.
For the high fail, as the resistance increases, the body voltage of a person with a wrist strap will increase. If the resistance is to high, body voltages can rise above 100 volts.

As I was not familiar with the Tester mentioned I wanted to look it up. The Hakko 498 Wrist strap checker seems very simple. However, I see no reference to any test methods the equipment complies with to provide some assurance to the user. I would also be concerned with the inability to adjust any of the pass/fail settings to meet those indicated within S20.20-2021 of < 3.5 x 10^7 ohms. Thus now the user has no way of knowing if its a true pass or fail without the actual reading being displayed.