https://beta.bandainamcoent.eu/en/cb/man-of-medan-for-free/confirmation
To clear up confusion, this is stated in the terms of service of the giveaway (page 2):
The duration is a total of four (4) calendar days. However, the participants accept that the Giveaway is operated by the ‘’first come, first served’’ rule as defined in the conditions of participation outlined below. Hence, the participants accept that the Giveaway might end before the end date of the Duration, due to this early closure.
The number of winners is one hundred thousand (100,000) and each winner will win the following: - One (1) Steam code to play the Video Game
The Winners will be chosen as follows: “first come, first served”. Therefore, the first participant to participate in the Giveaway will win one (1) Game key out of the total of one hundred thousand (100,000) game keys, the second participant will win one (1) game key out of the remaining ninety-ninethousand nine hundred ninety-nine (99,999) game keys and the one hundred thousandth participant will win the final remaining one hundred thousandth game key.
https://media-center.bandainamcoent.eu/games/man-of-medan/TDP-MOM-GIVEAWAY-RULES-EN.pdf
So the only issue with this giveaway is we don't know when the 100.000 participants has been reached. Which is perhaps also why they say 'if you are selected' (e.g. within the first 100.000). If my memory served right from similar previous giveaways, it should work out fine.