A question posed to the LARUG's LinkedIn group: Does revit have symbols for center line or angle like the other software has?
OK: select a dimension > hit Edit Type and look at the properties!!!
You should be able to figure it out from there... If not; look at the image below for the 3 "Centerline" fields and go at it (in Revit)!!!
More on Dimensional goodness, from an old post on Dimensions: Here!!! also...
A final tip: Unless you have memorized all parameters for all possible objects, ALWAYS CHECK THE PARAMETERS!!!
If you have a question and then look at all the parameters, both the Instance and Type, you just may find what you are looking for... or better yet, find something you weren't looking for yet that will help you immeasurably later on!!!