The Ninth Circuit in De Osorio v. Mayorkas held that the plain language of CSPA (Child Status Protection Act, see 8 U.S.C. § 1153(h)) provides for automatic conversion and priority date retention to aged-out derivative beneficiaries. This decsion is controlling in petitions with USCIS under the 9th circuit.
Before this case, when such beneficiaries aged out before their parents became permanent residents, a new I-130 petition filed by their parents for them would have a new priority date, which means they would have to wait many years before they can immigrate or apply for a green card (Permanent Residence Status), in some cases this can take over a decade. With this decision, the old priority date of the I-130 filed for their parents, for which they were derivative beneficiaries, would be retained. So that new I-130 that the LPR (lawful permanent resident) parent files for the aged-out son or daughter, could have that old 1985 or so priority date, speeding up the immigrant visa or permanent resident (green card) process by over 10 years in some categories.