Here's my solution.
Firstly IDs are generated for each entrant. RandInt function is used to generate random integer as Selection Sequence for each team.
The teams are separated into two groups (top 5 ranked teams and Other than top 5 ranked teams ).
Round 1: Top 5 ranked teams
After the teams are sorted by the Selection Sequence, the IDs are generated to join the entrants by Join tool.
Round 2: Other than top 5 ranked teams
After sorted the teams by the selection sequence, the teams are split into 5 groups by using Tile tool. Then the rows are filtered out if [Tile_SequenceNum] is greater than 5 (Each entrant take one team in Round 1. Thus, only 5 teams need to be taken in this round)
The teams are joined to entrants by using Join tool.
Lastly, the results of Round 1 and 2 are combined by using Union tool. That's it.