added comment for device cache capacity configuration

features/device-mgt/org.wso2.carbon.device.mgt.server.feature/src/main/resources/conf/cdm-config.xml

@@ -77,6 +77,9 @@
     <DeviceCacheConfiguration>
         <Enable>true</Enable>
         <ExpiryTime>600</ExpiryTime>
+        <!--This configuration specifies the number of cache entries in device cache. default capacity is 10000 entries.
+        This can be configured to higher number if cache eviction happens due to large number of devices in the
+        server environment-->
         <Capacity>10000</Capacity>
     </DeviceCacheConfiguration>
     <CertificateCacheConfiguration>