[css-lists-3] Mention that all increments and sets are processed, in order.

Author: fantasai

css-lists-3/Overview.bs

@@ -814,6 +814,11 @@ Manipulating Counter Values: the 'counter-increment' and 'counter-set' propertie
 		</pre>
 	</div>
 
+	If multiple instances of the same <<custom-ident>> occur in the property value,
+	they are all processed, in order.
+	Thus increments will compound,
+	but only the last set value will take effect.
+
 <h3 id="creating-counters">
 Creating and Inheriting Counters</h3>