InstancedBufferAttribute: Clarify meshPerAttribute.

docs/api/en/core/InstancedBufferAttribute.html

@@ -26,7 +26,7 @@
 
 		<h3>[property:Number meshPerAttribute]</h3>
 		<p>
-			Default is *1*.
+			Defines how  often a value of this buffer attribute should be repeated. A value of one means that each value of the instanced attribute is used for a single instance. A value of two means that each value is used for two consecutive instances (and so on). Default is *1*.
 		</p>
 
 		<h2>Methods</h2>