[SoLiDUS]

The red dotted people can only kill themselves upon the realisation that
they are marked: it doesn't count unless they know for sure. So if you've
got 7 people with marks, it would wait until the 8th day for everyone to be
sure.

Suppose you're one of 4 marked people: on the first day, you see 3 marks
and 26 unmarked. You wait until the second day and they are still around...
That can mean that the other 2 marks haven't yet realized that they are
painted. You wait until the third day: if there are only 3 marks, it should be
the decisive and on the fourth day, none of them will be alive. On the fourth
day, however, they're still around... which can mean only one thing: you are
also marked. On the fifth day, every one of you would die. This works for all
of the marked (same logic).

So, if the game ends on the 8th day, there were 7 people with marks. They
all died on the same day...