The math could be correct, or not. It all depends on the amount of participants, as others may do the math and see it as something negative, I would look at it differently (  Yes I know, I'm from the company ).

We do not force you to like/retweet a minimum amount, nor a maximum amount. If i do the math of time spent, by liking/retweeting 10-20 post a week, I can do that within 20 minutes. Those that spent the time to do the 2 custom retweets, will indeed gain their stakes faster.

All-in-all, the earlier you get into a campaign, the higher your chance is to earn above the average