How to find discrepancy between the number of files and recognized movies by plex?

[OttoKerner]

Mandatory reading https://support.plex.tv/articles/categories/your-media/naming-your-movie-media-files/

see also https://support.plex.tv/hc/en-us/articles/201543057-Why-is-some-of-my-content-not-found-

Several things to try:

1. filter your movie library with the ‘duplicates’ filter.
   If your files are named ambiguously, Plex recognises sometimes several different files as one and the same movie, due to this feature https://support.plex.tv/hc/en-us/articles/200381043-Multi-Version-Movies

2. install the WebTools plugin, which has a feature which lists ‘unrecognised’ files

3. search for file names in your movie folder which end in part2, cd2 or any of the other file name endings listed in this help article https://support.plex.tv/articles/naming-and-organizing-your-movie-media-files#toc-2
   Rename these or, even better, move each movie into its own properly named subfolder.
   Do avoid file names ending in partX. If ‘Part 2’ is in the official title of the movie, then append its file name with ‘optional’ information like the resolution or such, so that the last part of the file name is not part2. e.g. Harry Potter and the Deathly Hallows Part 2 (2011) - 1080p.mkv

4. file names containing certain ‘reserved’ words are ignored by Plex. Avoid these
   https://support.plex.tv/hc/en-us/articles/201381883-Special-Keyword-File-Folder-Exclusion
   If you want to add ‘bonus material’, you can do so, if you stick to the naming guide https://support.plex.tv/hc/en-us/articles/200220677-Local-Media-Assets-Movies

Sometimes, after renaming mis-matched files you have to perform the Plex Dance with the affected files, so the wrong match is purged from the Plex database.

Tip: you can use 3rd party software to assist you in cleaning up your file and folder names.
One such very useful product is Filebot
Don’t forget to set it to use the {plex} naming schema and do also take a look at the introductory videos.