The wife gets one eighth and the the remaining 7/8 must be divided into four equal parts, one part for every daughter and two parts is for the son. This is from the net wealth after paying back all dues on the deceased including the One third.
It is the right of every person to keep one third from all his net wealth after his death to be spent on any aim or person that he wants. This one third can be spent on charity, giving to family or friends or any other lawful purpose.
You can keep a part from that Third to your unmarried daughter which will added on her share from your inheritance.