What are the causes and implications of the warning "Too many figures [>15000] in a shadow overlap"?

edit

When this warning occurs, what is the result in the simulation? Is shading ignored for that timestep?

As advised in the warning message, I've used Output:Diagnositcs "DisplayExtraWarnings" to get additional information. An example of what that produced is here:

** Warning ** Too many figures [>=15000] in a shadow overlap
**   ~~~   ** Overlapping figure=Mir-POLYGON 2 OF BUILDING 1 - SHADING PLANE 55, Surface Class=[Detached 
Shading:Building]
 **   ~~~   **   This error occurred 1 times.
 **   ~~~   ** Figure being Overlapped=CIRCULATION10.1:CIRCULATION10.1_EXTFLOOR_1_10_0, Surface Class=[Floor]
 *************

And, I did read the related post here, which gives some ideas on how to reduce the likelyhood of this warning occurance.

Is this warning occurrence only related to large number of shading surfaces, or is it also more likely to occur with large number of building surfaces?

I have some ideas on how to reduce the Shading:Building:Detailed surfaces (currently ~150 in my model), but it would be difficult to reduce the BuildingSurface:Detailed surfaces (currently ~4100 in my model).