ATP Finals group winner tiebreaker rules?

[pabonaparte]

So Thiem and Nadal both win on Gameday 1.

Thiem beats Nadal on Gameday 2.

Set difference is now 4-1 for Thiem, 2-2 for Nadal. Who is this Group Winner if Thiem loses 0-2 and Nadal wins 2-0 on Gameday 3?

[Chaz22]

H2H kicks in then

[HeeeHAWWWW]

This link is useful, they always post all combos of outcomes:

https://www.nittoatpfinals.com/en/scores-centre/scenarios

[bleedblue]

Was hoping there could be some wild tiebreak scenarios.

Really curious if Medvedev will tank this match since he has to play again in 24 hours and this match is meaningless.