I have always done this in the past, go into the property manager and select the value to be changed and then click the feature and select the dimension that you want in the value area. For some reason the past three days this has been unavailable to me, is there an option that may have been turned off or did they get rid of this in the most recent SP? This was a great way for me to fix the TERRIBLE cut list feature that is constantly wrong and changing itself to continue to be wrong while I edit.
Just a tangent thought: PLEASE SOLIDWORKS FIX THE WELDMENT FEATURES!!! THERE ARE SO MANY BUGS WITHIN THEM I WILL NOT HAVE ANY HAIR IN 5 MORE YEARS!