There might be times when Excel takes what should be a number and treats it as text. This could happen after importing data, or entering data in a custom form. You might see a #NaN error (Not a Number). It’s sometimes fixable by formatting the cells as numbers, but Excel can be stubborn. The good news is it’s gotten better at not doing this, and there are three functions to use when it does. This video shows you how to use them.
Between the Sheets, Episode 80.