In roulette the number of bets are known as "inside" bets and the red-black, odd-even and high-low are "outside" bets. If you only bet the outside pots you have to bet at least a minimum for that table. For example if the placard says $5 minimum, that is the minimum bet you have to make on these outside spots. However, the inside numbers can have dollar bets on them providing all of your inside bets total at least $5.