Spot elevations are necessary for calling out the elevations of slabs, steps, base and top of structural items, etc.  But one simple checkbox can make them act very strangely… so beware.
 
Allow me to explain.
 
The other day a colleague was attempting to place spot elevations at the base and top of a ramp, but the spot elevation marker was telling him the floor was 19′-0″ above his head.  It should have been reading zero.  He tried revealing hidden elements…nothing there.  He looked for plan regions…none.  He looked high and low, but there was no logical reason for the spot elevations to be picking up the higher elevation.
 
Then we looked over at the view’s property settings.  There it was.  The view had the roof plan as an underlay.  The spot elevation was picking up the top surface of a roof slab that was indeed 19′-0″ above the current floor plan.  He simply turned off the underlay and the spot elevation worked just great.  So if you notice a spot elevation giving you some trouble, you give it some trouble right back…but first turn off the underlay!
 
Here is the same view as the image above, but with the roof plan as an underlay.  You can see the standing seam metal roofing; but if it had been a slab, it would have been quite invisible.

 
Happy Revitting