Yeah, I know it is not very scientific....but it works for me.
FYI, that is very scientific.

* the scientific method has five elements (goals, models, data, evaluation, revision),
* the scientific method is cyclic,
* the scientific method is a means of achieving progress toward a chosen goal.

GOAL: sharpen RSK Mk4 knife
MODEL: available angle settings on the lansky
DATA: visual examination for presence of sharpie mark
EVALUATION: if sharpie mark disappearing, you're sharpening edge
REVISION: change angle setting until you're sharpening

start with the smallest angle, increase until you're removing sharpie