If this is in an office environment, have you included the "Human factor" in your scripts. When an employee is irritated, or got up on the wrong side of the bed, or it is a Monday "people hate Mondays", or they just want to tick you off. What's to say they will not punch in the right numerical value but punch in an incorrect value, and when confronted, they simply reply "Oh! I must have punched the wrong one, sorry, I'll try not to do it again".
Or possibly this script has something to do with taming such attitudes.