Displaying data as time duration rather than time of day

I have a column of data that I would like to format as hh:mm:ss. The data indicates a length of time...I have tried all of the custom data options but all automatically change to the time of day when I double click on my cell(s). Seem like it should be a simple fix but I just can't seem to find the answer. Thanks!

Excel doesn't really understand the difference between "Elapsed Time" and "Time of Day". They're both the same thing.
Time is just a decimal number, a fraction of 1 day.
6 hours is 0.25 (6 devided by 24)

The time displayed is just cell formatting to make it look like a time to your eyes. But excel still just sees the real numeric value.
When you double click the cell, you're going into edit mode so it shows the whole time value without the custom formatting you put on the cell.

You can format the cell as hh:mm:ss to show only that, but the cell is still a time value, and excell sees it as such. So you will always see the AM/PM in the formula bar and in Edit Mode (double clicking a cell).

Thanks for the quick response! I am digitizing cassette tapes of interviews from the 90s and may end up transferring the data from my excel sheet into a database (not sure which one yet). My concern is that the durations (ex- 00:45:21, for a 45 min 21 second tape) may transfer as a time of day. I have about 700 tapes to digitize, so I want to make sure everything is represented as clearly as possible. Any thoughts, or do you think it's fine to leave it as is?