Why the num SUEntitiesGetNumInstances gets is 38 in SU model?

I develop a tool to exchange model information from SU to MFC in C++ SDK of Sketchup,
and I find the interface the number of instance which “SUEntitiesGetNumInstances” get is38, but I already deleted all instance in the model for test ,that is to say ,this model has not any face or line,but why the interface still get the number 38?

Can you post the model?