This is percentage change in total traded volume between 2 subsequent trading days. Suppose the total volume on Monday is 100 and on Friday it was 120, 1 day change in volume is calculated as (120/100) – 1*100 = 20%. A positive output indicates rising number of volumes whereas a negative change indicates drop in volumes.

Change in volume needs to be viewed in conjunction with price change and open interest change. Rise in price accompanied by increase in open interest and volume traded is a bullish signal. Rising price accompanied by falling open interest and volume as well as falling price accompanied by rising open interest and volume are both signals of bearish trend.