What experiments have you undertaken to find out for yourself? Have you looked at the manual? have you asked colleagues? Have you written a little program with a variable defined like that and looked at the compiler output to see how much space the compiler assigned it?
But i want to know how the size and length of data is assigned?
Did you start by looking at the data map output of the compiler to see how the compiler interpreted the PICTURE? If not, why not? Seeing what the compiler generated is usually a good way to understand any PIC clauses you don't understand.