Here's what's happening.
Kometa gathers all the movies in your library, and finds out from TMDB which TMDB collections contain those movies:
|====================================================================================================|
| Loading Collection File Default: franchise |
|====================================================================================================|
| |
| File Loaded From: /defaults/movie/franchise.yml |
| |
|========================== Building TMDb Collections Dynamic Collections ===========================|
| |
| Loading All Movies from Library: Filme |
| Loaded 1944 Movies |
...
| Mapping Name: TMDb Collections |
| Type: tmdb_collection |
...
| Keys (Title): |
...
| - 531242 (Suicide Squad Filmreihe) |
| - 1448577 (Columbia Classics: Volume 2) |
| - 266672 (Ted Filmreihe) |
Among the 295 collections returned from TMDB is a TMDB collection named "Columbia Classics: Volume 2", which has TMDB ID 1448577.