Simple addition of hours worked per day with result formatted as HH:MM

Hello Beginner here, 

Working with a fillable form PDF where the users will enter in the time it took to complete a task. For example, it took 2:59 for task one and 2:37 for task two. Where each time is written in HH:MM.

The total box is a simple addition but gives the result in total HH:MM.

Each task field Format tab is set to Time -> HH:MM. I have been using the Calculate tab and having it sum the select the fields from the form "Pick..."

However it simply adds the task times and results as 4.96. Where as I want it to result as 05:36.

When the Format tab is set to Time -> HH:MM, nothing is displayed however. 

Am I missing something in the Calculate or in the Format steps? Or maybe both?

Any help is greatly appreciated! Or maybe there is a section in the forums that I need to read. 

Thank you, 

Chris5C4D