Driver seven, and the only one of the nine that is decided by law rather than by the room. It is also the driver most people ignore, because on a good night it is a small part of the money. It is not there for the good nights.
What the tip credit is
Under federal wage-and-hour rules an employer may, in some circumstances, count a portion of an employee's tips toward the employer's minimum wage obligation. That arrangement is called a tip credit. Where it applies, the employer pays a reduced cash wage directly and the tips are credited toward the rest. The federal cash wage in that arrangement is $2.13 an hour with a maximum credit of $5.12, and if an employee's tips plus that cash wage do not reach the full minimum wage for the period, the employer must make up the difference.
Those are federal floor numbers, and for most bartenders they are not the operative ones. States set their own rules and may be stricter than the federal floor. Some states allow a tip credit at their own figures; a number of states require employers to pay the full state minimum wage before any tips are counted, so tips sit entirely on top of a full wage. The Department of Labor publishes the current position for every state in one table.