Richard S. Page, Metro's soon-to-depart general manager, is such a nice and competent guy that we hate to catch him making even a trivial error. But he did so in public on Saturday, when he described that day's opening of the Yellow Line shuttle as the eighth in the subway system's history. Turns out it's the ninth, with 42.4 route miles now being operated of the uncertain goal of a 101-mile system.

For Metro mavens, here in chronological order is the rundown of Metro openings:

Red Line, Rhode Island Avenue to Farragut North, 4.6 miles, March 29, 1976.

Red Line extension, Farragut North to Dupont Circle, 1.1 miles, Jan. 17, 1977.

Blue Line, National Airport to Stadium-Armory, 12.9 miles, July 1, 1977.

Red Line extension, Rhode Island Avenue to Silver Spring, 5.6 miles, Feb. 6, 1978.

Orange Line, Stadium-Armory to New Carrollton, 7.5 miles, Nov. 20, 1978, with initial service being operated as an extension of the existing Blue Line.

Orange Line extension, Rosslyn to Ballston, 2.9 miles, Dec. 1, 1979, with Blue and Orange Line service separated and eastbound Blue Line trains terminating at Stadium-Armory.

Blue Line extension, Stadium-Armory to Addison Road, 3.5 miles, Nov. 24, 1980.

Red Line extension, Dupont Circle to Van Ness-UDC, 2 miles, Nov. 5, 1981.

Yellow Line, Gallery Place to Pentagon, 3.2 miles, with service continuing over previously operated tracks from Pentagon to National Airport, April 30, 1983.

Don't try to add up these mileages. Because of rounding off the decimals, they wouldn't total precisely 42.4 miles.