Minoura b-60r gradient equivalent to resistance

Hi all, I just upgraded from Zpower to Power meter (crank). One of the benefit is i can add resistance now to my classic trainer (minoura b60r) when grade changes in Zwift. However, i would like to know the resistance level against the gradient in Zwift.

Anyone of you are using Minoura b60r?
This is my self-made resistance adjustment.

Gradient 0% = resistance level L
Gradient 1-3% = resistance level 1
Gradient 4-6% = resistance level 2
Gradient 7-9% = resistance level 3
Gradient 10-12= resistance level 4
Gradient 13-15 = resistance level 5
Above 15% = resistance level H

Any of you have better increments?

I would like to hear your thoughts about this.

Up… any one havr their thoughts? Thank you!