Hi !
Well, your Scene Coordinate System is in feet. You see the projection at the bottom of CE.
In general, I'd recommend you reproject your data in ArcMap before import in to CityEngine to the same NAD projection just in meters, not feet.
Or you adapt the extrusion height, but I'd recommend that because your overall scene size is the wrong.
Let me know if that all makes sense and if you have more questions !
Matt
p.s maybe create some test shapes and test extrusion into CE and export to GDB, then route back to ArcScene or so to check that you have full control over correct units. Once you have a stable workflow, you're good to go.