Super Mario 64 What does L is real 2401 mean?

It's really nothing, just a texture used as a "plaque" of sorts. On the star statue in the courtyard, it's really only there for decoration.

The writing on it is supposed to be illegible, and any rumors spawned by it are false.

The same texture appears later in Legend of Zelda: Ocarina of Time in Dodongo's Cavern.