Serial means a 56 cm frame measured from the center of the crank to some point above the seat tube/top tube juncture. The rest means it was built on February 24th 1988, so a 1988 model year bike. In this area, in decent condition, that bike is worth $250-350, even with the red tires, etc. Hard for my old eyes to tell actual condition from a single dark-ish picture, but if it's dirty as sin and not in great shape, half that.