As far as i know, it is the number of people who would join the lottery not put money in it.
Also, if some people won but decide not to participate, what will happen? Like, 20 out of 200 decided not to invest, so will they do another lottery to replace 20?
The site says that draw winners have no obligation to invest so I guess it is just a free roll?! It is a bit confusing to be honest.