That's the advertised CPM from the BBS and the other type is also like that sometimes it has increased by an person advertising and it's increment is about 1 to 2 points from 50 to 51,52 and when it's from BBS it's advertise more and we have seen it like 100 or of 150 CPM...the 50 or 51 CPM needs hard work to get payment and  💯 or 150 needs not hard work like 51 CPM value..so now it's on 50 and achieve it by doing hard work according to the relevant content...