2.1.995 Part 1 Section 188.8.131.52, NPER
a. The standard states if type is any number other than 0 or 1, #NUM! is returned.
Office treats nonzero values of type to indicate payment is at the beginning of the period.
b. The standard does not specify a default for the optional argument type.
In Office, if the value for type is omitted it defaults to value of 0.
c. The standard states that the argument type is truncated to an integer.
Office does not truncate the argument type to an integer.