YouTube Data API, why the number of comments does not match?

Why does the number of comments there show 21, but I counted 25 comments?Video id is cJzpeTurBxs. (https://www.youtube.com/watch?v=cJzpeTurBxs)

CASE 1https://www.googleapis.com/youtube/v3/videos?part=snippet%2Cstatistics&id=Jt_WxMC2jdM%2CcJzpeTurBxs&maxResults=50

response:

enter image description here

CASE 2https://youtube.googleapis.com/youtube/v3/commentThreads?part=snippet%2Creplies&key=googleAccessKey&maxResults=100&order=time&textFormat=plainText&videoId=cJzpeTurBxs

response:
enter image description here

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa