Choose the heirs who survive the deceased and enter the estate after debts and any will (up to one third). The calculator applies the fixed shares (furud) and the residue (ta'sib).
Fixed shares from the Quran (e.g. a wife takes 1/8 when there are children); the rest goes to residuary heirs, with a son taking twice a daughter's share.
Estate 24,000; heirs: wife, one son, one daughter. Wife 1/8 = 3,000. The remaining 21,000 splits 2 : 1, so the son gets 14,000 and the daughter 7,000.