A circle U is used in ASME, ASME Y14.41-2003 to be exact.It refers to the distance from the surface a profile tolerance is offset.  A distance of 0.000 means that the tolerance is bilateral.This does away with having to draw a phantom line to denote which side a profile tolerance is applied to.
If its not a standard in the ProE drawing call out make a symbol
From: -
To: -
Subject: [proecad] - New GD&T Profile Tolerance
Date: Wed, 2 Apr 2014 18:57:10 +0000
 
 
 
A new symbol,
circle U, was added to profile tolerance. In the past, a design
 engineer wanting to specify an unequal profile tolerance on the drawing would draw a chain line in the applicable area. Two arrows were shown to displace the tolerance zone. In the new standard, the circle U symbol follows the toleranced value in the profile
 feature-control frame. This announces that an unequal tolerance is in effect.
 
Is there some way to add this to the interface?
 
 
 
Regards,
 
  
Robert Altman
Manager, CAD Engineering & Tech Support