PostEaseImpressions are the least useful number on their own
An impression means a Pin appeared somewhere on someone's screen. It says nothing about whether it caught their attention. Treat impressions as context for the numbers below, not as a result to optimize for.
Saves and outbound clicks are the real signal
A save means someone found a Pin worth keeping; an outbound click means it moved someone toward an actual destination, a site or a product. Both say far more about whether a Pin is working than impressions or even the total number of people it reached.
Judge performance over months, not days
Since Pinterest keeps surfacing Pins for search intent long after they are published, a Pin's first-week numbers are a weak preview of its real performance. Check a Pin's totals a few months after publishing rather than a few days, and you get a far more honest read on whether it is working.