BP pointed me to Ticket Lead Time parameter which was crucial to understand the functionality of this plugin. Lead time can not be 0 then you get unexpected results. The functionality is following. When you create a ticket with recurrence ”Lead time” = 4, “Concurrent active tickets” =1, “Pattern” =Yearly, Every 5 January and “No end date”, the recurrent ticket will occur only on 1st January with Due Date on 5th January.