That's the prize money for simply playing in that round of the Cup. I'd say you're very lucky to be drawn in a higher level Cup. If you go to the league standings tab, and go to the Cup, you can see the prize money for each stage of the Cup. That's the money you get for each leg of each stage, so you'll get another +/- 2M for the second leg whatever the result, and if you go to the next round, you'll get more than 2M for each leg of that round.