Please prefer to attach actual example files (.odt in this case) over images/sreenshots if not the issue is expressly concerning the view.
This problem may look trivial, but actually is due to a fundamental shortcoming of spreadsheets: They don't offer a standardized way to enter durations (differences in time).
In addition there is a very bad practice to find everywhere: The colon-separated formats specifically standardized for TimeOfDay values are misused to communicate durations (or time spans).
Closely related to this second problem we find the
extremely bad habit to try to express a duration of (e.g.) "23 min 10 s" as "23:10". This is
definitely inacceptable because the relavant specification of colon-separated formats (by proper authority: ISO) expressly states that shortened formats always
must start with the hours part.
Thus you are (practically) forced...
1. to enter durations in the TOD format actually deprecated for the purpose.
2. to NOT omit the starting 00: (or 0:) for the hours.
In addition you may want to add a delay which shifts the resulting TOD to the next day , and there is no accepted format for the display of the result in such a case. To get that correctly, you would
need to enter and display the starting point in time as a DateTimeStamp.
Note: If you want to use the traditional non-decimal subdivions of a day into 24 hours, of an hour into 60 minutes, and of a minute into 60 seconds (going back to the earliest days of calendaric astronmomy) you are forced to stick to the underlying "unit" day (d) in spreadsheets. This ignoring the fact that engineering and science wouldn't do so, because the calendaric day isn't of constant length (on the level of precision we currently assume granted).
See attached example: