Forced mate in 106?

Stockfish says that there's a forced mate in 106 moves after move 53 in this game. What is the sequence? How do I calculate it lmao

Also what's the biggest number you've seen in an engine saying there's a forced mate?

Endgame TB says DTM 46 (plies, 23 moves)

#1 When in doubt, attempt to defend against SF (with as many takebacks as you want) and see if it can prove that a mate exists.

Sorry, I'm not familiar with the acronym "DTM". What does it mean?

DTM = Distance to Mate, or how many moves will transpose (assuming perfect play from both sides) until checkmate.

I actually played it out with SF and I checkmated in move 75