The word "fifth" is afraction. Alternate translation: "At harvest time you will divide the crops into five parts. You will give one part back to Pharaoh for payment and the four parts are for your own" (See: [[rc://en/ta/man/translate/translate-fraction]])
You can state clearly the understood information. Alternate translation: "for food for your households and for food for your children" (See: [[rc://en/ta/man/translate/figs-ellipsis]])