update documentation

Author: mawinter69

README.md

@@ -45,11 +45,12 @@ Via the "Edit" button one can edit existing maintenance windows (and also add an
 Going to "Manage Jenkins->Agent Maintenance" will present you a list of all currently defined maintenance windows of all agents.
 Using the button "Add" allows to use a label expression to select a list of agents for which to apply the maintenance window.
 
-##### Recurring maintenance windows
+## Recurring maintenance windows
 It is also possible to define recurring maintenance windows. Using a cron syntax you can specify the start time of the downtime and a duration.
 Recurring maintenance windows are added as planned maintenance window 7 days before they start by default. This way you can easily cancel or modify them before
 they start. The lead time for adding recurring maintenance windows can be changed by setting the system property com.sap.prd.jenkins.plugins.agent_maintenance.RecurringMaintenanceWindow.LEAD_TIME_DAYS
-during start up of Jenkins. Note that changing the lead time can have unwanted side effects like duplicated maintenance windows.
+during start up of Jenkins. Note that changing the lead time can have unwanted side effects like duplicated/missing maintenance windows. 
+
 Changing a recurring maintenance will not change already scheduled maintenance windows for it. Those need to be adjusted manually.
 
 ## Best practices