Actually "Maximum number of processing files" setting means that it will process up to 2 files per one run.
Dolphin runs video processing every 5 minutes (via cron jobs).
The problem maybe with big video files, if they are processing longer than 5 minutes:
for example you uploaded 5 big video files and processing of one file takes approximately 15 minutes, and cron runs every 5 minutes:
- after 1st cron run you will 2 files in processing and 3 files are pending processing
- after 2nd cron run (after 5 minutes) you will have 4 files processing and 1 file pending processing
- after 3rd cron run (after 10 minutes) you will have 5 files processing and 0 files pending
- then after 15 minutes you will have 3 files processing
- after 20 minutes 1 file processing
- after 25 minutes all video files should be ready
To limit the server load you can set to run video processing every 30 minutes (in table sys_cron_jobs)