Time format Tata steel 2024

Hello,

I have a question about the time format in the Tata 2024 tournament. I've searched for the answer but couldn't find it. Maybe someone here knows.

The format is: 100 minutes for 40 moves, 50 minutes for 20 moves, 30 sec. increment.

What I don't get is the '20 moves'-part. What is the purpose of that? After 40 moves you get 50 minutes and when the time runs out it's over. In my opinion is doesn't matter if it's move 42 or move 81.

Someone?

The time control is 100 minutes for 40 moves, followed by 50 minutes for 20 moves.
There is also a 30-second increment after each move.

So you start with 100 minutes and you get 30 seconds extra per move starting before move 1.
If you have completed your 40th move, then you get an extra 50 minutes. If you have completed your 60th move, then you get an extra 50 minutes. And so on on 80th, 100th move...

That could explain it, but if you look at the game Giri - Gukesh from round 4 they didn't get an extra 50 minutes after move 60.

Update: They changed the time control from '50 minutes for 20 moves' into '50 minutes extra after move 40' on screen during the livestream.