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."
Lastly, if the numbers still aren’t adding up, you can look at adjusting your fixed expenses. Doing so will be much more difficult and require greater discipline, but on close inspection a "need" may just be a “hard to part with.” Such decisions come with big trade_offs, so make sure you carefully weigh your options. Tip: Small savings can add up to a lot of money, so don’t overlook the little stuff. You might be surprised at how much extra money you accumulate by making one minor adjustment at a time.