(4)Synthetic excess spreads can be designated in two different ways. One way is through providing credit enhancement to the senior or the mezzanine tranche. A second way is through providing credit enhancement to all the tranches, including the first loss tranche. Where the synthetic excess spread provides credit enhancement to the senior or mezzanine tranches only, it cannot be treated as a first loss tranche. The retainer should therefore retain at least a minimum amount in all the tranches to comply with Article 6(3), point (a), of Regulation (EU) 2017/2402. Where the synthetic excess spread provides credit enhancement to all the tranches, the synthetic excess spread should be equivalent to a first loss tranche of the synthetic securitisation, and, thus, be deemed to comply with Article 6(3), point (d), of Regulation (EU) 2017/2402.