Show how the balance before payment value of R733760.42 for month 1 was calculated

Month 1 Balance Before Payment = (Month 1 Sales) - (Month 1 Expenses)

Month 1 Sales = R735000
Month 1 Expenses = R1639.58

Month 1 Balance Before Payment = R735000 - R1639.58
Month 1 Balance Before Payment = R733760.42