1D change in call open interest is calculated as percentage change between current days call OI and the previous days call OI. Suppose current days call OI is 113 and the previous days call OI is 100, 1D change in call OI is 13% ((113/100) – 1)*100.
A positive change in call OI indicates that more people have bought call contracts compared to previous day. This suggests that participants are bullish on the stock. On the contrary if the output is negative it indicates that investors have squared off their open positions and are not confident about the future price rise.