How does an individual score over 10,000 DL points in one day?

That is suspiciously a lot for one individual. If a player serves their 2 league-reward drinks as their 4th and 5th cup, 40 and 50 points respectively, and all 14 team members drink them, they'll get 1350 points. If they are a fast Magic Eye player, they might earn another 2000-3000 points playing Spot the Difference. If they clear a load of Spear Grass, they can get more on top of what they earn completing HW tasks. Even so, 10K seems hard to reach, legitimately.