When ATC tells you for an example: Finnair 90, turn Left heading 040.
You as a pilot turn 040 via the Autopilot but on the A/P it doesn’t say 040 but rather heading 40, which is also correct but the OP here wants the A/P to show 040 NOT 40.
Or 050 not 50, 030 not 30. It’s supposed show a 3-digit number not 2-digit as it is today. Because when ATC tells us to head for a specific heading, they say it in 3-digits and we pilots respond in 3-digits but eh A/P shows HGD: 10, 20, 30, 40, 50, 60, 70, 80, 90 Not 010, 020, 030, 040, etc…
It can get confusing for some people to see 2-digits instead of 3 when ATC clearly says 3 but in my honest opinion, it doesn’t matter much to me since 020 degrees and 20 degrees are the same thing.