Replace: "Summary: Calculate the amount received at maturity for a fixed interest security per 100 currency units of face value." with "Summary: Calculates the amount received at maturity for a zero coupon bond." For semantics, replace current sentence and formula with: "The return value is: Investment/(1-Discount * YEARFRAC(Settlement; Maturity; Basis))" Also, replace "Basis: the type which indicates how the year is to be calculated by days; see section 3.11.6" with "Basis: the day count basis used in this calculation; see section 3.11.6