Filled in MultiMesh instance_count doc.

doc/classes/MultiMesh.xml

@@ -91,7 +91,8 @@
 		<member name="custom_data_array" type="PackedColorArray" setter="_set_custom_data_array" getter="_get_custom_data_array">
 		</member>
 		<member name="instance_count" type="int" setter="set_instance_count" getter="get_instance_count" default="0">
-			Number of instances that will get drawn. This clears and (re)sizes the buffers. By default, all instances are drawn but you can limit this with [member visible_instance_count].
+			Number of instances that will get drawn. This clears and (re)sizes the buffers. Setting data format or flags afterwards will have no effect.
+			By default, all instances are drawn but you can limit this with [member visible_instance_count].
 		</member>
 		<member name="mesh" type="Mesh" setter="set_mesh" getter="get_mesh">
 			Mesh to be drawn.