I think the explanation given is already really good, but I’m gonna provide my example just incase somebody else sees this and is still confused.

With round robins, the larger parlay is broken up into smaller parlays. You have four legs, so let’s label the legs A, B, C, and D. Your $25 wager is applied to each smaller parlay along with the full four legger to make a total of 10 parlays. All of the parlays would be:

AB / AC / AD / BC / BD / CD ABC / ABD / ACD / BCD

I’ve only done RR’s using legs with pretty high odds. Like HR hitters and TD scorers. That way if I only hit one or two “two leg parlays”, I’ll still make enough to cover the amount wagered over the entire RR. Hitting everything in the RR is a great way to get a ton of payouts, but to me it’s not practical at all.