A "memory schedule" is also known as a clock face schedule is one where the train (or bus for that matter) comes consistently at the same minutes past the hour for each departure and intermediate stop. I take a bus that runs every 60 minutes from my home to work sometimes, it leaves at :03 minutes past the hour, and runs hourly. This means I don't need to consult a schedule to see what time exactly the bus is coming whether I'm taking the bus at 8:00am, 9:00am or in the afternoon.
All 10 Pacific Surfliner departures now leaves San Diego at exactly 0:01 minutes past the hour between 4:01am and 9:01pm. They make nearly all intermediate stops at the same time into Los Angeles, except for the two trains that stop at San Clemente Pier which make stops from San Juan Capistrano through Los Angeles, 3 minutes later (this extra stop adds 3 minutes to the timetable).
This may seem small but it makes scheduling connecting buses a lot easier, for example, all trains stop at Santa Ana at 0:01 minutes past the hour - in both directions (except for one southbound train that isn't clockface and stops at 11:11pm and there is a note that this is temporary due to trackwork). Ideally all connecting local buses - even those that run hourly - could pulse in Santa Ana arriving at lets say :55 minutes past the hour and leaving again at :05 minutes past the hour, allowing local transit riders to make transfers and also having very short efficient connections (assuming Amtrak's running on time) to and from the Surfliner, with minimal time waiting for connections and efficient door-to-door transit trips.
I know the transit scheduler who did all of the North County Transit District Schedules, and the Coaster went to a "memory schedule" (it's a little less consistent than the Surfliner's because of extra peak-hour trains) a few years ago, and this made it much easier for him to schedule short connections between Breeze local buses and Coaster commuter trains, I don't know how much this applied to Amtrak.
