R. Eliezer says: "Then she shall go out free" — when she is a bogereth; "without money" — with signs (of puberty). We are hereby taught that (in the absence of signs) she goes out by deducting from the value (of the years served to the value of those to be served.)
Rabbi Eliezer Reads Without Money as Code for Something Else Entirely
Mekhilta Tractate Nezikin 3:31