Dear Niladri,
Absence days or Hours will be calculate as per WS Rules means 13.08 to 16.08 you have 3 days working & 1 day off for 15 that's why Absence days as 3 & hours as 24,
If you want to display 4 days & 32 hours in Absence days & hours then you need to make 15th Aug as working day.
Counting rule settings are for calculating Quota days, so as per you are getting quota used days as 4 days.
Hope this will clarifies you.