Judging from last year's final results they likely draw in pairs to create the two groups. They put 1 and 2 seeds into a hat and then draw them out so one goes into one group and one into the other. This is repeated for the next two (3 and 4) the next two (5 and 6) and the final pair as well.
It is possible that you could get a result as in 1,3,5,7 and 2,4,6,8 but that is just one result and you can see from last year's draw that it was not exactly like this.
In 2006 it was 1,3,5,8 and 2,4,6,7.
so the last pair was reversed.