Update docs for additional_metadata re: filtering semantics (#3670)

Author: luislee818

frontend/docs/pages/v1/additional-metadata.mdx

@@ -73,6 +73,24 @@ For example, you can filter events by the `source` metadata keys to quickly find
 
 ![Blocks](/addl-meta.gif)
 
+## Filtering Semantics
+
+When filtering **runs** with `additional_metadata`, Hatchet returns runs that match **any** of the provided pairs (logical `OR`), not all of them.
+
+<Callout type="info">
+  For example, filtering runs with `{ first_name: "john", last_name: "doe" }`
+  returns runs whose metadata matches *either* `first_name: "john"` *or*
+  `last_name: "doe"`, not only runs that match both.
+</Callout>
+
+Event filtering behaves differently: filtering **events** with multiple `additional_metadata` pairs requires all pairs to match (logical `AND`), since events use `JSONB` containment under the hood.
+
+<Callout type="info">
+  For example, filtering events with `{ first_name: "john", last_name: "doe" }`
+  returns only events whose metadata matches *both* `first_name: "john"` *and*
+  `last_name: "doe"`.
+</Callout>
+
 ## Use Cases
 
 Some common use cases for additional metadata include: