If you carry a credit card balance, the minimum payment is a "need" and it counts toward the 50 percent. Anything extra is an additional debt repayment, which goes toward this 20 percent category. If you carry a mortgage or a car loan, the minimum payment is a "need" and any extra payments count toward "savings and debt repayment."
You might choose to break down your expenses even further, between things you need to have and things you want to have. For instance, if you drive to work every day, gasoline probably counts as a need. A monthly music subscription, however, may count as a want. This difference becomes important when it’s time to make adjustments.