If your subtitles are early or late by that amount:
ffmpeg -ss 00:00:00 -i sone443engsub.mp4 -t 00:15:56.510 -c copy clip_015651.mp4 sone443engsub convert015651 min better
It uses a frame-accurate reference that prevents the "lag" often seen in long-form subs. Resource Allocation: If your subtitles are early or late by