Calculating a duration help


Hi everyone!

I’m wanting to determine how long it take a team member in my office to complete a task. Ideally, this would be from a “creation date” (Start Time) until a date of completion (End Time) in “days and hours”. The other feature is that we only work during the week so I don’t want to skew the results if there is a weekend or holiday in between the start and stop time. Here’s what I have so far but the results are showing as 0:00. Thanks in advance!