Performance Tuning for query with Semi Monthly Date Ranges, Sql Server

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create table testsalesvolumetable (crediteddate datetime not null, amount int not null)
insert into  testsalesvolumetable values 
 ('20161201',1) ,('20161202',1) ,('20161203',1) ,('20161204',1) ,('20161205',1)
,('20161206',1) ,('20161207',1) ,('20161208',1) ,('20161209',1) ,('20161210',1) 
,('20161211',1) ,('20161212',1) ,('20161213',1) ,('20161214',1) ,('20161215',1) 
,('20161216',1) ,('20161217',1) ,('20161218',1) ,('20161219',1) ,('20161220',1) 
,('20161221',1) ,('20161222',1) ,('20161223',1) ,('20161224',1) ,('20161225',1) 
,('20161226',1) ,('20161227',1) ,('20161228',1) ,('20161229',1) ,('20161230',1) 
,('20161231',1) ,('20170101',1)

/* ----- without variables */
    declare @psv int;
    select @psv = Sum(amount)
      from testsalesvolumetable
      where crediteddate >= dateadd(day, (1- (day(convert(date,getdate()))/16)) - (day(convert(date,getdate()))%16), convert(date,getdate()))
        and crediteddate <  case 
        when day(convert(date,getdate()))>15 
          then dateadd(month, datediff(month, -1, convert(date,getdate())), 0) 
        else dateadd(day,15,dateadd(month, datediff(month, 0, convert(date,getdate())), 0))
        end;
        
    select psv=@psv;
    --*/

/* ----- with variables */
    --declare @psv int;
    declare @currentdate date;
    /* change to date datatype to get rid of time portion*/
      set @currentdate = getdate(); 
      --set @currentdate = '20161212'

declare @fromdatetime datetime;
    declare @thrudatetime datetime;
      set @fromdatetime = dateadd(day, (1- (day(@currentdate)/16)) - (day(@currentdate)%16), @currentdate);
      set @thrudatetime = case 
        when day(@currentdate)>15 
          then dateadd(month, datediff(month, -1, @currentdate), 0)
        else dateadd(day,15,dateadd(month, datediff(month, 0, @currentdate), 0))
        end;
    select @psv = sum(amount)
      from testsalesvolumetable
      where crediteddate >= @fromdatetime
        and crediteddate <  @thrudatetime;
 --/*
    select 
          psv=@psv
        , CurrentDate =convert(varchar(10),@currentdate ,121)
        , FromDateTime=convert(varchar(10),@fromdatetime,121)
        , ThruDateTime=convert(varchar(10),@thrudatetime,121);
    --*/

View schema
Execution time: 0,02 sec, rows selected: 7, rows affected: 32, absolute service time: 0,19 sec