The simplest way to put it is that you just have to put money in the atm and wait. Any money you put in on a round won’t be counted toward the dividends until the a full round has past after putting the money in (I.e. money out in on round 6 won’t provide dividends until the transition into round 8). A bit thing to note about this is that you’re looking at playing a game into at least the 70s to get this challenge done (earliest I’ve seen it done so far is 69 in the discord).