Legacy Recurring Intervals (First Charge Interval & Subsequent Charge Interval) only exist for legacy Accounts who enrolled prior to July 7, 2019 and are separate from Recurring Cycles. If these parameters are used, then you must not enable recurring cycles. Accounts enrolled after July 7, 2019 will only be able to see recurring cycles. If you see both of these options in your setup, it is highly recommended you proceed with recurring cycles moving forward.