Scoring is relative to other anomalies. The yellow one right after seems more egregious (less probable and thus higher scoring) than the ones circled. Additionally, there is a difference between what an anomaly is scored when the anomaly happened (in real-time) versus what it might be scored as later (after a more egregious anomaly is seen). You can tell by looking at the "initial score" of an anomaly:
More info on scoring: Machine Learning Anomaly Scoring and Elasticsearch - How it Works | Elastic Blog