Description:
Having a field formatted as [HH]:MM the value of which has been calculated from two other fields formatted as HH:MM and one field formatted as [HH]:MM the result misses one minute if it is negative.

Steps to Reproduce:
1. Format Field A1 as [HH]:MM and set it to 08:00
2. Format Field A2 as HH:MM and set it to 08:15
3. Format Field B2 as HH:MM and set it to 15:30
4. Format Field C2 as [HH]:MM and set formula B2 - A2
5. Format Field D2 as [HH]:MM and set formala to C2 - A1

Actual Results:
The result in field D2 is 00:44

Expected Results:
The result in field D2 should be 00:45


Reproducible: Always


User Profile Reset: Yes


OpenGL enabled: Yes

Additional Info:
If B2 is set to 16:30 the result is correct: 00:15 (as with all positive differences)

If you changes the [HH]:MM formattings to [HH]:MM:SS you will see that exactly one second is missing (result is 00:44:59 instead of expected 00:45:00).


About LibreOffice:
Version: 6.2.0.3 (x64)
Build-ID: 98c6a8a1c6c7b144ce3cc729e34964b47ce25d62
CPU-Threads: 4; BS: Windows 6.3; UI-Render: GL; VCL: win; 
Gebietsschema: de-DE (de_DE); UI-Sprache: de-DE
Calc: threaded