The preliminary ratings assigned to the prime floating-rate residential mortgage-backed securities (RMBS) to be issued by Perpetual Trustee Co. Ltd. as trustee for Progress 2023-1 Trust reflect the following factors. The credit risk of the underlying collateral portfolio (discussed in more detail under "Credit Assessment") and the credit support provided to each class of rated notes are commensurate with the ratings assigned. Credit support is provided by subordination, lenders' mortgage insurance (LMI), and excess spread, if any. Our assessment of credit risk takes into account AMP Bank Ltd.'s underwriting standards and approval process, which are consistent with industrywide practices, the servicing quality of AMP Bank (discussed in more detail under "Origination And Servicing"), and the support provided by the LMI