can't take out anything

Disce quod ignoras: Marsi doctique Pedonis
saepe duplex unum pagina tractat opus.
Non sunt longa quibus nihil est quod demere possis,
sed tu, Cosconi, disticha longa facis.

Learn what you don't know: one work of (Domitius) Marsus or
    learned Pedo
often stretches out over a doublesided page.
A work isn't long if you can't take anything out of it,
but you, Cosconius, write even a couplet too long.

—Martial