added comments

src/de/tud/kom/p2psim/impl/analyzer/metric/filter/MergeDeliveryRatioFilter.java

@@ -33,7 +33,8 @@ import de.tudarmstadt.maki.simonstrator.api.common.metric.Metric.MetricValue;
 /**
  * calculates the delivery ratio, which is the percent of actual transferred
  * messages. (1 - overhead). Uses the duplicate and message count metrics and
- * merge them.
+ * merge them. Used metrics are in DELIVERY_RATIO_LIST and duplicate metric must
+ * end with "Dup".
  * 
  * @author Simon Luser
  * @version 1.0, 08.03.2017