Future Dated Data in Salesforce
As noted in the Metric Builder, by default Ambition defers processing future-dated data.
Deferred processing is by design to prevent issues with systems that create tasks/events years out into the future.
If Metric values are lower in Ambition than your internal reporting and your source-of-truth values contain records with future-dated data, deferred processing is most likely causing the disconnect.
The good news is that deferred processing is an internal setting that can be changed to rectify the issue, reach out to email@example.com to find out more.