Auto Generate Seconds Counter in time portion - sql server

select Service,
       Subscription_Number,
   Order_Status,
   Service_Type,
   Data_Plan,
   Carrier,
   MDN,
   Usage,
   DATEADD(SECOND,ROWNUM,period_end_date) as sequence from
(
select Service,
       Subscription_Number,
   Order_Status,
   Service_Type,
   Data_Plan,
   Carrier,
   MDN,
   Usage,
   ROW_NUMBER() OVER(ORDER BY Usage ASC) as ROWNUM,
   period_end_date
from
(
SELECT [Service]
      ,substring([Subscription_Number],8,7) Subscription_Number
      ,[Order_Status]
      ,[Service_Type]
      ,[Data_Plan]
      ,[Carrier]
      ,[MDN]
      ,round(ISNULL([Usage],0),2) Usage
  ,DATEADD(MONTH, DATEDIFF(MONTH, -1, GETDATE())-1, -1) as period_end_date
  FROM [dbo].[test_Usage]
  where upper(Service) <> 'TOTAL'
  --order by Subscription_Number desc
  )A
  )B