How do you reduce the space between a poem and the poemline-counter

In the documentation of the verse-package, it says: »By default the numbers are typeset at the distance vrightskip into the right margin.«

Therefore it is possible to change this length, e.g.:

documentclass{scrartcl}

usepackage{fontspec}
usepackage{verse}
usepackage{libertine}

begin{document}

setlength{vrightskip}{-15em}

begin{verse}setcounter{poemline}{1137}poemlines{5}
τὰν ἐκ πασᾶν τιμᾷς 
ὑπερτάταν πόλεων 
ματρὶ σὺν κεραυνίᾳ· 
καὶ νῦν, ὡς βιαίας ἔχεται 
πάνδαμος πόλις ἐπὶ νόσου, 
μολεῖν καθαρσίῳ ποδὶ Παρνασίαν 
ὑπὲρ κλιτύν, ἢ στονόεντα πορθμόν.
end{verse}

end{document}