Think of roles, positions and groups as a filter - these settings restrict who gets to see the published content.
Position vs Role
Position is the most restrictive filter because it uniquely identifies one person. There can only be one player in position 3. When you publish content to position 3 it's only that single player who'll get in.
Roles allow you to exercise multiple teams at the same time and send content to every player that has the same role.
If you have five teams of the same type, then publishing to Role 3 will generate 5 messages - one to each player that's in Role 3 for each of the 5 teams.
Jan has a single team of 8 players. Each player should receive content that's unique to their role in the team.
TeamXp's "Roles" allows up to 5 roles but since this is for exercising multiple teams and here we have only one team, we can use Position to uniquely identify each player role.
Everyone remains as Role 1 (which is the default) but the team roles are identified using Position