No predictions loaded for 1993. This site serves NOAA predictions from its own store, and this period has not been fetched for Potrero Point yet. Nothing is estimated or interpolated in its place. NOAA's own page for the station has the official table: tidesandcurrents.noaa.gov.
tidealmanac.site/us/ca/potrero-point-9414334/1993
Potrero Point, CA tide table 1993 (printable) · Tide Almanac