Tricky russian statistic problem

There is a game they played in Russia where a person marked 6 entries in a table 6x9 where all 54 numbers were listed sequentially. After many round one statistician noticed the people from Moscow, Leningrad, and Novosibirsk (3 cities with the most educated population) had higher proportion of large payoffs than participants from other regions in proportion to the number of tickets sold.

How did this happen?

So I was trying to find the numbers that had the highest probability of being selected but dont they all have the same probability??