In addition to the late charges referred to above which are intended to defray Landlord’s costs resulting from late payments, any late payment of Rent shall, at Landlord’s option, bear interest from the due date of any such payment to the date the same is paid at the Default Rate, provided, however, that if Landlord imposes a late charge on any overdue payment, such overdue payment shall not begin to bear interest under this Paragraph 18.4 until thirty (30) days after the due date thereof.