fix sentence

Author: LadyBluenotes

src/routes/reference/basic-reactivity/create-resource.mdx

@@ -92,10 +92,10 @@ interface ResourceOptions<T, S = unknown> {
 - **Type:** `ResourceSource<S>`
 - **Default:** `undefined`
 
-Reactive data source whose value, when coerced to a boolean, determines whether the fetcher runs. 
-If the value is truthy, it is passed as the first argument to the fetcher. 
-If the value is falsy (including `undefined`, `null`, `false`, `0`, `""`, or `NaN`), the fetcher will not be called. 
-Once the source changes to a truthy value, the fetcher automatically re-runs.
+Reactive data source evaluated before the fetcher runs.
+When the value is `undefined`, `null`, or `false`, the fetcher is not called.
+Otherwise the current value is passed as the first fetcher argument.
+Each change to a truthy value triggers the fetcher again.
 
 ### `fetcher`
 
@@ -268,4 +268,4 @@ const [user] = createResource(() => fetchUser(), {
 
 // user() is never undefined
 console.log(user().name); // "Loading..." initially
-```
+```