After importing music into a library , the album gets a number.
The Very Best of 10cc [443]
How to prevent this
https://beets.readthedocs.io/en/latest/reference/pathformat.html#aunique
Any group of albums with identical values for all the identifiers will be considered “duplicates”. Then, the function tries each disambiguator field, looking for one that distinguishes each of the duplicate albums from each other. The first such field is used as the result for %aunique . If no field suffices, an arbitrary number is used to distinguish the two albums.