For LP bonds such as FIDL-BUSD bond, the RFV is calculated differently because the protocol needs to mark down its value. Why? The LP token pair consists of FIDL, and each FIDL in circulation will be backed by these LP tokens - there is a cyclical dependency. To safely guarantee all circulating FIDL are backed, the protocol marks down the value of these LP tokens, hence the name risk-free value (RFV).