If you are working with the day from the Gift Created Date for the schedule day of month (so that you can indicate that all payments for a gift created on June 15, 2023 will be made on the 15th of the month for subsequent months) you will need to use the field settings on the Schedule Day of Month field to do so.
To begin, select the 'Gift Created Date' as your Source field for the Schedule Day of Month field. Then select the Field settings (circled in red below).
Use the option to Extract the day from the incoming date format (shown below). You will need to use a custom format (select 'Enter your own format' to do so) with the custom formula: M/d/yyyy h:mm:ss tt
