Hot to see which files where backed up?

This is amazing. Acronis does not provide any support and the forums are worthless?

If it's a file backup, 'fast incremental' option is used and full cataloging is enabled, you may try search in catalog by modification date to see whole list of files that were changed within this range and thus included in the backup (not counting open files that are included anyway). Otherwise it will be impossible. If 'fast incremental' is not used it's still possible to try it, but files that are changed (and included in the backup) without changing modification date, may not show up in search.

Thanks. We are talking about DISK backup, not file.

Particular case is: Disk/Volume backup of Disc 1, partitions FAT16 Dell Diags, C: (Windows) and D: (Data). The most recent FULL backup was taken on Sat. 3/8, 65 GB. The first incremental ran on Mon. 3/10 and created a TIB of 11.6 GB. Bear in mind that the Customer do not wok on weekends, there is no Exchange on premises and therefore not much files changes are expected specially because we are not backing up HIBERFIL or PAGEFILE.

When I clink on that TIB I found something I can't explain (see attached image): A list of "Backups" that go from 3/9 to 3/13. Having taken the full on 3/9 I click on the "backup" for 3/11, select C: and see ALL folders and by curiosity got into on that is being zipped for years and never ever used, nevertheless changed it: C:\DELL. Why is an unchanged folder being backed up? Why multiple "backup" dates after the TIB was created?

Thanks in advance

Clicking on a tib file displays all backups in the chain (starting from the full - files that differ only by a number at the end of their names). Clicking further will show not the files that this particular incremental backup contains, but what will be recovered from this incremental. So if it was present when the backup was created, it will show up even if physically it is located only in the base full backup.
With disk backup you can try the method with search in catalog too, however some files may be left unnoticed if they are modified without changind date (e.g. if they were open)

Thanks for the explanation. Can you please elaborate on "try the method with search in catalog too"?

See my first comment. If 'full' cataloging method is used, you can go to the vault -> data view -> and search with 'modification date' criteria to match files modified since the backup before the last.

It's also possible that backup switched sector-by-sector mode (it may do so in case of corrupted FS. Logs may contain warning about it) or exclusion stopped working (do you have exclusions set in the plan?)