UC and Statutory Maternity Pay how show Earnings

Hello i have problem with fill UC form - Work and Earnings section. I have SMP [Statutory Maternity Pay] and that only what i getting, no more earnings and not sure how i should put that to form. If i getting SMP and i put amount there i still have to put something in usually earning cant write 0.00 , what i should write there?

Please help

Thank you