Add clarification on reportAllChanges

README.md

@@ -265,7 +265,9 @@ _**Warning:** do not call any of the Web Vitals functions (e.g. `onCLS()`, `onFI
 
 ### Report the value on every change
 
-In most cases, you only want the `callback` function to be called when the metric is ready to be reported. However, it is possible to report every change (e.g. each layout shift as it happens) by setting `reportAllChanges` to `true` in the optional, [configuration object](#reportopts) (second parameter).
+In most cases, you only want the `callback` function to be called when the metric is ready to be reported. However, it is possible to report every change (e.g. each larger layout shift as it happens) by setting `reportAllChanges` to `true` in the optional, [configuration object](#reportopts) (second parameter).
+
+_**Important:** `reportAllChanges` only reports when the **metric changes**, not for each **input to the metric**. For example, a new layout shift that does not increase the CLS metric will not be reported even with `reportAllChanges` set to `true` because the CLS metric has not changed. Similarly, for INP, each interaction is not reported even with `reportAllChanges` set to `true`—just when an interaction causes an increase to INP._
 
 This can be useful when debugging, but in general using `reportAllChanges` is not needed (or recommended) for measuring these metrics in production.