Track numbers with characters to filename

[Furbell]

This works for lossless files but doesn't seem to work properly for MP3's.
https://imgur.com/a/L1C3XdT Image 1
The MP3's seem to report being tagged as track number/total tracks
Image 2
However looking at it in foobar shows that TRACK is only the track number, and total tracks is separate
Image 3
It seems this applies to MP3's using normal track numbers as well
Image 4

Is this perhaps an issue with the way foobar tags things and the way mp3tag tags/reads them?

Is there a tag for total track number? (iTunes: track 3 "of 10")

In iTunes, if I have an album of 10 tracks, my tracks will be numbered 1 to 10, but in the "Get Info" box for each track, it will say "Track 1 of 10," "Track 2 of 10," etc. It's that second number I'm wondering about. What if I have, say, 10 individual tracks from am album that actually has 11 tracks. What is the name for the tag to which that "11" refers, and can I modify that with mp3tag? Thanks.

says %totaltracks% is the field, but this shows up as empty when I try to use it in mp3tag on both FLAC and MP3

Sorry, had to link to the imgur album since new users are limited to 2 links per post