elevation dimension in rcp

Hi there,

I am trying to use an elevation dimension in my rcp view (a 3D document view) to the show height of a roof at the points where it meets the wall. My issue is that the elevation dimension is showing a negative value and is also showing the incorrect height from project zero (the correct elevation to project zero is 166540). Refer to below image. How would I approach fixing this or what is a recomended approach to showing the roof elevation on an rcp.