Connection management Historical details

we are trying to get the connection management historical data from dba_hist_sys_time_model view .

We are referring one off the script to get data for connection management historically , below is script :

select e.stat_name "Statistic Name"

, (e.value - b.value)/1000000 "Time (s)"
, decode( e.stat_name,'DB time'

             , to_number(null)
             , 100*(e.value - b.value)
             )/
     ( select nvl((e1.value - b1.value),-1)
     from dba_hist_sys_time_model  e1
        , dba_hist_sys_time_model  b1
     where b1.snap_id              = b.snap_id
     and e1.snap_id                = e.snap_id
     and b1.dbid                   = b.dbid
     and e1.dbid                   = e.dbid
     and b1.instance_number        = b.instance_number
     and e1.instance_number        = e.instance_number
     and b1.stat_name             = 'DB time'
     and b1.stat_id                = e1.stat_id
)
     "Percent of Total DB Time"
  from dba_hist_sys_time_model e


     , dba_hist_sys_time_model b


 where b.snap_id                = 2221
   and e.snap_id                = 2222
   and b.dbid                   =376520799
   and b.dbid                   =e.dbid
   and b.instance_number        =1
   and b.instance_number        =e.instance_number
   and b.stat_id                =e.stat_id
   and e.stat_name              ='connection management call elapsed time'

above script gives output but when scripts are provided in range of snap i.e for collecting all together i am trying to provide value of snap_id in between clauses it is giving me some weird data .