The field GIFT_fld_Schedule_WeeklyDayOfWeek is a bitwise field that assigns the following values to each day of the week:

1 - Sunday
2 - Monday
4 - Tuesday
8 - Wednesday
16 - Thursday
32 - Friday
64 - Saturday

Adding the above values together will allow you to utilize any combination of days.  For example, a value of 4 is used for a gift that occurs only on Tuesdays while a value of 66 (2 + 64) occurs on both Mondays and Saturdays.