Update README.md

Author: Helene

README.md

@@ -7,7 +7,7 @@ The ***IBM Spectrum Scale bridge for Grafana*** could be used for exploring IBM
 Grafana Bridge is a standalone Python application. It translates the IBM Spectrum Scale metadata and performance data collected by the [IBM Spectrum Scale performance monitoring tool (ZiMon)](https://www.ibm.com/support/knowledgecenter/en/STXKQY_4.2.3/com.ibm.spectrum.scale.v4r23.doc/bl1adv_PMToverview.htm) to the query requests acceptable by the [Grafana integrated openTSDB plugin](https://grafana.com/docs/features/datasources/opentsdb/).
 
 
-![](/docs/bridge_overview.PNG=250x)
+![](/docs/bridge_overview.PNG=500x)
 
 ## Setup