The frame count getted from FFmpeg is different from its splitting action result?

Question

I had executed these two commands, and I got confused by its unconsistent result.

1. I got frame count through the command following:

   ffprobe -v error -count_frames -select_streams v:0 -show_entries stream=nb_read_frames -of default=nokey=1:noprint_wrappers=1 FPS30-536-CFR.mp4

   The result is 536.

2. I fetched every frame and saved it to a directory:

   ffmpeg -i FPS30-536-CFR.mp4 ./frames/out%04d.jpg

   I got 537 pictures in the ./frames directory which numbers form 0001.jpg to 0537.jpg

I had tried another video, the two results are maintained the same.

Please give me some hints, thank you very much.

Here is the video.