The calibrations for accuracy are basically zeroing in on the steps per mm for the axes. Your machine has to be mechanically adjusted first, which you have done. It’s just a ratio of two numbers. What you want/ what you get. You multiply that by the number in the $100 and $101 for the x and y axis. For instance if you want x to go 10mm and it goes only 9mm, then 10 / 9=1.111 and you’d multiply that by the number you now have set for $100. It requires an accurate measuring device and you may have to do it a few times to zero into the most accurate setting.
To view your settings in GRBL, you’d enter $$ in the console line. In Easel, you’d go to machine/advanced/machine inspector. You will see the console line box.
I don’t use easel, but UGS does the same thing. You just enter $$ in the command line and a window with all the GRBL settings comes up. Then to change one (as an example the x axis steps per mm) you type $100= " whatever number you need" and hit enter.
I’d write down what you have now so you can always go back if things go haywire.