I would only add to @NeilFerreri1’s advice by saying you’ll get a more precise value by calibrating over large distances. Start by using short distances (i.e. no more than a few inches, as you’re already doing), that way you don’t accidentally cause the machine to crash when it tries to move 45 inches instead of the 30 you commanded. When you get things dialed in fairly close at those distances, then go for longer ones, and you can make the minor adjustments (i.e. compensating for +/- 0.1 inch on a 10, 20, or 30 inch move).
Also, your $100 and $101 values will likely be slightly different. Part of the reason most X-Carve owners go through this procedure is because none of us will be tensioning our belts precisely the same, so the number of belt teeth across the entire length of either axis isn’t constant across all machines (or between axes even on the same machine). This also means you’ll generally end up with a very small amount of “skew” as the y-axis moves further away from machine-zero (the “bottom” of the work area), as either y-axis belt is likely going to be tensioned slightly differently.
This video has been shared several times before on the forum. It’s a great how-to.