The Deal Engagement Score number is calculated by combining the activity engagement performed on the Opportunity with anonymized, aggregated model data.

A big reason a score may not be reflective of the actual engagement with a deal is most likely due to a lack of key engagement data that influences the score. 

If your Deal Engagement Score seems inaccurate, confirm the following: 

• Zero stakeholders attached to an opportunity: If this comes up, suggest they go and add stakeholders to their opportunities. 
• Users are not Lofting their activities:  If this comes up, suggest that their team lofts their activities on a frequent and consistent basis