reword message

docs/src/test-assertions-js.md

@@ -254,7 +254,7 @@ Note that by default `toPass` has timeout 0 and does not respect custom [expect
 
 You can extend Playwright assertions by providing custom matchers. These matchers will be available on the `expect` object.
 
-In this example we add a custom `toHaveAmount` function. Custom matcher should return a `message` callback and a `pass` flag indicating whether the assertion passed.
+In this example we add a custom `toHaveAmount` function. Custom matcher should return a `pass` flag indicating whether the assertion passed, and a `message` callback that's used when the assertion fails.
 
 ```js title="fixtures.ts"
 import { expect as baseExpect } from '@playwright/test';