Document overriding the estimate limit

guides/introduction/installation.md

@@ -29,3 +29,18 @@ plugins: [
   ...
 ]
 ```
+
+## Customizing Estimates
+
+Options for internal `Oban.Met` processes can be overridden from the plugin specification. Most
+options are internal and not meant to be overridden, but one particularly useful option to tune is
+the `estimate_limit`. The `estimate_limit` determines at which point state/queue counts switch
+from using an accurate `count(*)` call to a much more efficient, but less accurate, estiamte
+function.
+
+The default limit is a conservative 50k, which may be too low for systems with insert spikes. This
+declares an override to set the limit to 200k:
+
+```elixir
+{Oban.Met, reporter: [estimate_limit: 200_000]}
+```