Changepoint issue

[waystogetthere]

Hi, I have some questions about the column: 'changepoint'.
According to my last post(thanks Kaster! you're really helpful!) : https://www.kaggle.com/datasets/yuriykatser/skoltech-anomaly-benchmark-skab/discussion/325533, the changepoint should indicate the status changing between 'normal' and 'anomaly': i.e. 'normal' to 'anomaly' or 'anomaly' to 'normal'.

However, when I checked the data, I found something unexpected.

I merged all .csv file under data/valve1/ and sort them by the column: datetime. There are 63 records with changepoint = 1, but only 32 indicate a status switching.

[waystogetthere]

The image above shows 2 columns: changepoint and anomaly. While I can see that during collective anomalies there are some changepoints = 1

[waystogetthere]

if we look in detail (from 10am to 11am, 09 March), it is clearer.