In my opinion,

F = Delta_P x Ai x DLF.

What the surge report gives you is maximum surge pressure (or peak pressure) P in chart result. And P0 is steady state pressure (or operating pressure) which is available from line list or can be read from chart at Time O seconds

Delta_P (maximum unbalanced surge pressure) can be taken from chart result (by using formula Delta_P = P - P0) or detail discussion with process.

If using P = P0 + Delta_P for calculating F will give you a very big value which leads to unnecessary over design of pipe support or pipe over stress

Looking for other opinions