When specified and set to 'Y', it indicates that the first calculation period should run from the effective date to the end of the calendar period in which the effective date falls (e.g. Jan 15 - Jan 31 if the calculation periods are one month long and effective date is Jan 15.). If 'N' or not specified, it indicates that the first calculation period should run from the effective date for one whole period (e.g. Jan 15 to Feb 14 if the calculation periods are one month long and the effective date is Jan 15.).