Does anyone have a calculator for Marlin's Autotemp routine?

Does anyone have a calculator for Marlin’s Autotemp routine? I’ve seen conflicting formulas for the conversion between print speed and temperature. I’m trying to get a range between 205 and 270 for ABS on my printer and would like to calculate the ideal S,T and F values.

Through experimentation, I’ve found that S205 T280 F8 gets close to the result, but when I calculate what that should be based on the formula’s I’ve found, it says I should be getting a range between 300 and 1000!