Help me with calculation part.....

i want monthly/yearly consumer consumption report based on service no

if i select month then MAX of cumkwh @23:59:59 of that month and MIN of cumkwh means @00:00:00 = Consumption (screenshot 1 for reference here initial reading and final reading is taking 24 hrs of timestamp) but i want exact timestamps means @00:00:00 and @23:59:59

if i select year i want 12 records

for each month i want the consumption separately.

i'm attaching screenshot and tableau workbook in latest version.

Thanks,

surya