Understanding views sources

Twitch offers you to understand “where did my views come from” after a stream.
It breaks it down into 3 categories : Twitch, Channels et External.

I have one simple question :
Why is the total number of views of a stream not equal to the sum of the views coming from Twitch, Channels and External ?

In my last stream, I got 10k total views with 6k coming from Twitch, 100 coming from Channels and 100 coming from external. Is that a bug ? Or is there a missing source of views explaining where do the remaining 3,8k are coming from ?

Thanks in advance for your help

This counts “unique”

This does not