If you click the button to Use This, you can use it a bit like a vlookup in Excel.
Unfortunately, you can’t use this in the form version though, you have to Use it.
Enter a value in the first box and an ascending list of values in the second. It will tell you the number of the first row which is larger than the entered value.
For example, if you enter 10, and the values 9, 11, 13, it will return the number 2 (because 10 is less than the 2nd value in the list).