Extruder calibration simply ensures that 100mm requested = 100mm extruded. This simply guarantees that your extrusion multiplier will be the same across any (calibrated) printer, and will be comparable to the instructions given to others.
If calibrating hot, heat your hot end to printing temp and remove the nozzle.
If calibrating cold, remove your nozzle or hot end.
Extrude a small amount to ensure that your extruder motor is loaded and holding filament.
Take a ruler (or calipers) and place a piece of tape or get a marker ready at the 120mm mark.
Where the filament enters the filament runout tube, pull your filament as straight as you can against the ruler/calipers. Transfer the tape to mark 120mm.
Extrude 100mm. If doing this hot, watch to make sure the plastic isn’t shooting out to the side (partial clog) or showing signs of skipping.
To tell the printer to extrude, you can use the App or Printer Display (M5) to extrude 100mm at a time. If calibrating hot, make sure your extrusion temperature is set to that filaments default print temp.
Measure how much is left. Subtract it from 120 and note the value for later. Example: if I had 21mm left, 120mm - 21mm = 99mm actual extrusion.
Calculate your new e-steps using this formula: <new_e-steps> = <current_e-steps> * ( 100 / <actual_extrude_distance> )
In the AnkerMake App, go to the Device Settings>About Device. Press and hold down on EITHER the Version number or the word Version for 5-10 seconds (Try the other if the first doesn't work)
A new beta menu will appear at the bottom of the screen. Open that menu, go to motor pulse, and your current e-steps value is in the ‘E0’ Field.
With your new value activated, mark and extrude again. It often takes a few iterations to dial in.
When using the formulas above, make sure you’re using your updated e-steps value for the “current” value. Don’t keep using the original value.