SELECT
CAST(DATEDIFF(HH,localTime,serverTime)-1  AS VARCHAR) +'-'+
    CAST(DATEDIFF(HH,localTime,serverTime)  AS VARCHAR) [Hours],
COUNT(*) [Count]
FROM your_table
GROUP BY CAST(DATEDIFF(HH,localTime,serverTime)-1  AS VARCHAR) +'-'+
    CAST(DATEDIFF(HH,localTime,serverTime)  AS VARCHAR)

select diff_hours,count(diff_hours) from (select 24 * (to_date(LocalTime, 'YYYY-MM-DD hh24:mi') - to_date(ServerTime, 'YYYY-MM-DD hh24:mi')) diff_hours
from T_TIMETABLE ) group by diff_hours order by diff_hours;