Andrew S. Tanenbaum Edition 5th Exercise 3 Question 23 (Page No. 253)

Question

Imagine a sliding window protocol using so many bits for sequence numbers that
wraparound never occurs. What relations must hold among the four window edges
and the window size, which is constant and the same for both the sender and the receiver?

Answer 1

as here it's asking about the relation between window edges 

i.e upper bound and lower bound of the array in the sender and receiver side