Officially it is the UC top 9% guarantee policy

It ensures a place at a UC campus, most likely ucm, maybe ucr. But it does NOT guarantee admission to a specific major or a competitive campus, even like usd/ucsb/uci.  

There are two paths for 9%:  Statewide Path (9% statewide) + Local Path (top 9% in your HS), either one will get you the 9%-gurantee.  You can check your Gurantee status after submitting your UC application in the portal.

In practice, the number is  higher than 9%  in our HS for past years.