On the extruder calibration (e-steps) calculator, there is a calculator form.
Inputting the following values:
- Previous E-steps as reported by M92:
100
- Measurement between extruder entry and mark on filament (mm):
40
Yields:
Your new E-steps should be 125.00000
That's an increase of e-steps when the extrusion is too little.
From the klipper documentation:
rotation_distance = <previous_rotation_distance> * <actual_extrude_distance> / <requested_extrude_distance>
that is -
66.667 = 100 * (120 - 40) / 120
It looks like the logic is incorrectly reversed.