ad param to setTargetingForAst() (#1357)

* ad param to setTargetingForAst()

* update method info

* update method info

* changed wording a bit

* update param type and descp

dev-docs/publisher-api-reference.md

@@ -529,12 +529,17 @@ setTargetingForGPTAsync(adUnit, pickInViewDiv);
 
 <a name="module_pbjs.setTargetingForAst"></a>
 
-### pbjs.setTargetingForAst()
+### pbjs.setTargetingForAst(adUnitCode)
 
-Set query string targeting on all AST ([AppNexus Seller Tag](https://wiki.appnexus.com/x/PgOXBQ)) ad units.  Note that this function has to be called after all ad units on page are defined.  For working example code, see [Using Prebid.js with AppNexus Publisher Ad Server]({{site.github.url}}/dev-docs/examples/use-prebid-with-appnexus-ad-server.html).
+Set query string targeting for AST ([AppNexus Seller Tag](https://wiki.appnexus.com/x/PgOXBQ)) ad unit(s).  Note that this function has to be called after all ad units on page are defined.  For working example code, see [Using Prebid.js with AppNexus Publisher Ad Server]({{site.github.url}}/dev-docs/examples/use-prebid-with-appnexus-ad-server.html). If the function is invoked without arguments it will set targeting for all adUnits defined.
 
 **Kind**: static method of [pbjs](#module_pbjs)
 
+{: .table .table-bordered .table-striped }
+| Param | Scope | Type | Description |
+| --- | --- | --- | -- |
+| adUnitCode | Optional | `String or Array of strings` | Code(s) of the adUnit(s) for which targeting is being set. Omitting this parameter will set targeting on all adUnits. |
+
 <hr class="full-rule">
 
 <a name="module_pbjs.renderAd"></a>