Installment due date is based on the first purchase transaction date
If the purchase occurred in the first 15 days of the month, your due date will be the 1st of the next month.
If the purchase occurred in the last 15 days of the month, your due date will be the 16th of the next month.
In case of proceeding with more than one purchase transactions, all installments due date will be the same as the first transaction date.