What function to use to display a # value if under or over a specific number?

HELP!

Calculating time cards I need a function to display the value if the time is before 8.00 and another function to display the value if the time is over 16.50

So if the time is 7.71, I need a function to display that the time is 0.29
Or if the time is 17.76, I need a function to display that the time is 1.26