He could only make one team, considering that if you do 12-9, you are left with 3, and Jason wants to have his team consisted of 9 players. However, if you make 3 teams with 4 players on each team, or 4 teams with 3 players on each team, you could do that as well.
I'm not sure how to explain it but imagine looking at a soccer ball with a smiley face drawn on it. I mean thats its definition its hard to explain it without using its word in a sentence.