⬢Move the head and printbed in a way that printhead is in the corner.
⬢With a regular business card (250g), check the distance between the tip of the nozzle and bed.
⬢Adjust the height of the bed with the adjuster ring. You should be able to easily slide the business card between the nozzle and the bed with a little bite. We call it Al dente ;-)
⬢After adjusting, alway compress the bolt against the blue frame under the printbed. Gravity is not always enough to settle it after adjusting.
⬢Repeat for all 4 corners.
⬢YOU ARE DONE!