How do you interpret the total buy and sell volumes?

How do you interpret the total buy and sell volumes? It does not seem to be cumulative and at the end of the active trading session after 3:30 pm, one scrip was showing this:

Total buy quantity 157539
Total sell quantity 0

What does this mean?

Also, during the active trading session, the buy and sell volumes do not match. If 1000 shares have been bought, they must have also been sold. What accounts for the difference?

Check this

http://tradingqna.com/4601/there-any-indicator-track-total-volume-and-total-sell-volume

Refer to this link which I have come across : https://www.dynamiclevels.com/en/nifty/open-interest-nifty-future

IMHO, neither of these answers are relevant. The one by Arpan is not clear and the other one is about open interest in Nifty futures.
Yesterday and today (22-23 Aug 2016) There is a major sellof in Wellspun due to it losing out on business from a large US-based customer (Target). I see a large sell quantity and buy quantity 0.
Also, market depth shows several offer prices and no bid prices.
But, if the shares are changing hands, don’t there need to be buyers?