You can measure or look up your tablet's active area dimensions and use a little math to figure out how to convert inches to counts. Just divide the maximum count number by your tablet's size to get the counts per unit of measurement.
I don't have specific numbers but here are some random ones as an example.
Let's say the "right" number maxes out at 14,000 and your tablet's width is 6 inches. That's around 2,333.33 counts per inch (14,000 / 6).
Based on the numbers you said earlier, I'm assuming you were using an area of 3 x 4 inches?
Multiply both of those numbers by the counts per inch number you found earlier, it should stay consistent for both width and height. Using my random numbers:
3 * 2,333.33 = 7,000
4 * 2,333.33 = 9,333
Assuming you keep the top and left values set to 0, you can just set your right and bottom values to the numbers you get. You can change the top and left values to be something other than 0, but the difference between their counterparts (bottom and right) need to remain the same. In the example I used, the difference between left and right will always need to be 7,000 and the difference between top and bottom will need to be 9,333.