# Difference between open interest and volume?

From Nism series 8 workbook

An open interest is the total number of contracts outstanding (yet to be settled) for an
underlying asset. The quotes given above show us on August 9, 2010 Nifty futures has
an open Interest of 32062850. It is important to understand that number of long futures
as well as number of short futures is 32062850. This is because total number of long
futures will always be equal to total number of short futures. Only one side of contracts
is considered while calculating/ mentioning open interest. On August 8, 2010, the open
interest in Nifty futures was 30959200. This means that there is an increase of 1103650
in the open interest on August 9, 2010. The level of open interest indicates depth in the
market.
Volumes traded give us an idea about the market activity with regards to specific
contract over a given period – volume over a day, over a week or month or over entire
life of the contract.

As I understand the volume gives the no. of contracts traded over a period of time and Open Interest gives the number of outstanding contracts. What I am unable to understand is that why the 2 numbers never tally up if u consider a given time frame.
For E.G
On 23/07/19 for for INFY AUG Futures
At 930 am
OI - 18068400
Vol - 1655

At 1030 am
OI - 21301200
Vol - 5047
So there is an increase of vol - 3392, however, the OI has increased by 32,32,800 contracts . As per the definition, for every trade the volume should increase and the OI may stay flat, increase or decrease. Hence, not able to understand how to tally these numbers. Any help will be useful.

I got the answer . Divide OI by lot size.