An accurate extruder rotational distance tuned for your specific extruder head is critical, if off so will all of Klippers extrusion calculations. This should be done before other tuning and calibrations relating to extruding filament.

The recommended method is known as “measure and trim”. We have a current starting point from which to run our tests, the current value defined in printer.cfg, to use as an initial guess for the rotation distance so we don't need to obtain if from steps_per_mm or by inspecting the hardware. It's the same value you'll be changing after calibration.

Example printer.cfg:

[extruder]
rotation_distance: 31.4

Klipper describes the the process in this chapter of the documentation devoted to rotational distances.

Ellis's Tuning Guide provides a detailed explanation and covers the canonical process for tuning the value. See https://ellis3dp.com/Print-Tuning-Guide/articles/extruder_calibration.html

The best video resource for demonstrating this process is 00:02:22 into this YouTube video by Wild Rose Builds.