Recalculating a metric does the following:
Note: A Metric item will only be updated if any of the values in the metric changed.
There are five ways for you to recalculate metrics:
Click Items | Update Project Metrics.
Click OK.
Note: To speed up the Manual Recalculate process, you can add the below as a Quick Launch link to the Recalculate Project Metrics page.
_layouts/15/BrightWork/UpdateMetrics.aspx?ListName=Project%20Metrics&Source=../../../default.aspx
See the How can I edit the quick launch? help article for assistance on making this change.