Why Official stream said map diff 6/6 will win 7/7

I'm confused in these rules.
Helpppp pls

Because they lost less maps.

idk

lez [#2]

Because they lost less maps.

But they won more right?
Or they only count the lost point
less lost = better?

I thought it 7-7=0 6-6=0 and they're equal

Is it same 0? And we need to see round diff?