why?

Just ask one to get it rerolled.

SG removes your entries for games you win, but does not hide them from GA list. Even more as it is DLC GA Steam API will not return it as owned by you even if you activate it, so it will never be filtered on it's own from SG. You must have won 1st GA, got all your entries removed, then you manually entered GA for stuff you already won. Or if you used bot and bot entered without you realizing then not manually but automatically, but same story.

Good practice is that if you come to SG and see you won something - hide all GAs for this game in the first place so you don't reenter them by mistake. You can do this by clicking crossed-eye icon next to game name. Another good practice is to ALWAYS check whether you don't already own the DLC before entering any DLC GA.

What zelghadis said. The current system should remove additional entries after a win to prevent that kind of thing. So you won it and then it would appear you (or your bot) entered more giveaways for it and won one of those. Nice job!

But congrats on your good luck, they both appear to have had a few hundred entries. Statistics now dictates you won't win for month. (You can't argue with math.)

why

did you enter the same giveaway after winning it 11 hours ago?