The extent to which one is an arsehole. A quantity of arsehole-ness, i.e. having or being of greater arseholery simply means that the subject is more of an arsehole.
"Alternatively, you can get yourself a wedding planner, which is the wedding equivelant of debt consolidation. Rather than dealing with various different arseholes of varying levels of arseholery, you can get yourself one 18-carat, stone cold wanker." - Ed Byrne