The number of threads for update_binaries. If you notice that you are getting a lot of parts into the missed_parts table, it is possible that you USP is not keeping up with the requests. Try to reduce the threads. At least until the cause can be determined.
The number of threads for backfill.
The number of threads for releases update scripts.
Maximum simultaneous additional-processing workers and NNTP sessions. Workers reuse their process and connection across bounded batches; raise this only within CPU, memory, disk I/O, and provider connection limits.
The number of threads for nfo postprocessing. The max is 16, if you set anything higher it will use 16.
The number of threads for video metadata postprocessing. This includes movies, anime and tv lookups.
The number of threads for fixReleasesNames. This includes md5, nfos, par2 and filenames.