Media Type: .m4a file
Tag Version written: MP4
Tag Version in Usage: Did not notice before writing the tag.
I have attached screenshots for the above. Also, I noticed that it seems like the track number is actually written with a leading '0'. However, when displaying the tag using Mp3Tag and foobar2000, only the digit number of the track is displayed (that is, 4 from the attached screenshot, and not 04).
Let me know if you need more details, I would be happy to help.