Adding a buff to increase critical multiplier

On the pathfinder character sheet, how do you create a buff that will add to the critical multiplier.  While my barbarian is in accurate stance his crit multiplier goes from a x3 with his great axe to a x4.  What do I add the +1 to? Currently it is as such, however not sure if the crit confirm part is right either +4 to attack +8 to crit_confirm +1 to ???? for critical multiplier Thank you

That probably isn't a buffable stat.  The easiest would be to just make another attack entry to use when in that stance that has the correct multiplier.