Measuring and old experience

i struggled for 1 year and a half in endmyopia i did things wrong and though i could get away with it. i never added astigmatism for closeup so i struggle at night like now and yeah this is a backstory.I have booked an appointmet at an opticians im from uk. I will use their readings and decrease sph by .50 and ill leave astigmatism for now., normally they overcorrect by .25 so thats why im reducing by 0.5 I know how to active focus fine. I have learnt a lot about eyes now about rugby ball how astigmatism means at axis I need more correcition. my question is how to cm measure.? I have always used snellen for measuring because cm is confusing. I have astigmatism, i dont know what my real edge of blur would be since there are 2 kinds of blur its likely to make mistakes. please help

Check these posts, don’t worry about the size of the pic, focus on full clarity vs. blur.
No need to print, you can do it on the screen, too.

Instructions:

Just the wheel in a better pic on its own: