1D change in put open interest is calculated as percentage change between current day’s put OI and the previous day’s put OI. Suppose current day’s put OI is 89 and the previous day’s put OI is 75, 1d change in put OI is 18.67% ((89/75) – 1)*100. 

A positive change in put OI indicates that more people have bought put contracts compared to previous day. This indicates that market participants expect the price of the stock to fall and are buying put options to protect the downside to the stock. On the contrary if the output is negative it indicates that investors have squared off their open put positions and are not fearful about the price fall.