[FFmpeg-user] ffmpeg output messages

[JD]

Hi all,
(using  ffmpeg version 4.2.2 Copyright (c) 2000-2019 the FFmpeg developers).
what does it mean when ffmpeg (during transcode)
belches out:
bitrate=1366.8kbits/s dup=0 drop=133  speed=0.404x

So, if there were 0 duplicates, why drop 133 frames?
And what does the message mean?
Should I specify a higher fps?