User blog comment:Kogath/Monster Hunter 4 Ultimate for the Nintendo 3DS/@comment-24231002-20141021203826/@comment-5933391-20141021223104

Actually the numers in parenthesis is the weapons "real power". Basically it lets you compare the power of weapons that are different classes and do damage calculations. It was actually used in game for MHP3rd.

The great Gaijin Hunter himself actually did a post on it http://gaijinhunter.tumblr.com/post/56142405516/understanding-effective-weapon-power