Will this be another unfair attack on MPs with families?

Below is a FOI that seeks to scrutinise or expose MP's London accommodation. Why 307 MP's (Liberal + Labour?) not 650. Is someone playing games? MP's with families entitled to an extra room may well end up being the target of another anti-MP campaign because they will be the one's at the top of any league table.

The London allowance is around c£1,400 pcm for a single person and c£1,800 pcm