Help required on F&O Data of Nifty 50 CE June'19 Expiry

#1

Hi guys, I wanted to understand that in the attached screenshot, which is a screenshot of the NSE contract wise data for Nifty50 CE June’19 monthly expiry. On 13th Aug 2018, 33 contracts were traded, the number of options per contract are 75 so the total number of options should be 2475 in the OI column. But -150 is the number mentioned in the last column which is the OI column.

Does this mean that out of the 33 contracts that were traded, some were bought and some were sold and the net subtraction of OI was -150?

#2

Yes Volume is total traded contracts

And OI change will consider how many initiated, how many squared off