public int getBaseInstanceCount() {
        if (instanceSpan == 0) {
            return 1;
        }
        return getNumElements() * instanceSpan;
    }
Returns the number of 'instances' in this VertexBuffer.  This
 is dependent on the current instanceSpan.  When instanceSpan
 is 0 then 'instances' is 1.  Otherwise, instances is elements *
 instanceSpan.  It is possible to render a mesh with more instances
 but the instance data begins to repeat.

@return the number of instances
jme3-core/src/main/java/com/jme3/scene/VertexBuffer.java