Thank you

I'm studying this indicator because I think it may help me with an important idea that I have, but there's a problem - I noticed many times that only the latest open bars are accurate - when the candle closes, the red histogram bars change from what they just showed 1 second ago before the candle close. This seems to happen randomly or I don't understand why. So basically all past histogram bars on this indicator not exactly representative/reliable data, just the current open bars are. If you could explain how this indicator works, I would really appreciate it. Thanks