The COLUMNS function is fully automatic. When you provide a range to COLUMNS, it will return a count of all columns in the range. In the example, the formula in F6 returns 2, because there are 2 columns in the range B5:C10:
=COLUMNS(B5:C10) // count columns
COLUMNS counts the number of columns in any supplied range and returns a number as a result. For example, if we provide all of row 1 in a range, Excel returns 16,384 the total number of columns in an Excel worksheet.
=COLUMNS(1:1) // returns 16384
To count rows in a range, see the ROWS function.