Update derived loader example to be clearer (#509)

Author: azf20

website/pages/en/developing/assemblyscript-api.mdx

@@ -321,8 +321,8 @@ The following code will load the `Token` entity that the `Holder` entity was der
 
 ```typescript
 let holder = Holder.load('test-id')
-// Load the Token entity that the Holder entity was derived from
-let token = holder.tokens.load()
+// Load the Token entities associated with a given holder
+let tokens = holder.tokens.load()
 ```
 
 #### Updating existing entities