further clarification for aria-setsize

add that aria-setsize/posinset should also calculate value as if the attributes were not set, if they were provided the empty string.

clarify that aria-setsize should return indeterminate for any value set that is not a positive whole number

core-aam/index.html

@@ -9859,8 +9859,7 @@ <h3>Group Position</h3>
             specified by the author as either &quot;0&quot; or a negative number, [=user agents=] SHOULD use &quot;1&quot; instead.
           </p>
           <p>
-            If the <a class="property-reference" href="#aria-setsize"><code>aria-setsize</code></a> property is specified by the author as either &quot;0&quot; or a negative number, the author is
-            indicating the set is an indeterminate size. [=User agents=] MUST NOT calculate the set size of an indeterminate set.
+            If the <a class="property-reference" href="#aria-setsize"><code>aria-setsize</code></a> property is specified by the author as any string value other than a positive whole number, the set is an indeterminate size. [=User agents=] MUST NOT calculate the set size of an indeterminate set.
           </p>
           <p>
             If <a class="property-reference" href="#aria-level"><code>aria-level</code></a> is not provided or inherited for an element of <a class="termref">role</a>
@@ -9869,7 +9868,7 @@ <h3>Group Position</h3>
             following the explicit or computed <code>RELATION_NODE_CHILD_OF</code> relations.
           </p>
           <p>
-            If <a class="property-reference" href="#aria-posinset"><code>aria-posinset</code></a> and <a class="property-reference" href="#aria-setsize"><code>aria-setsize</code></a> are not provided,
+            If <a class="property-reference" href="#aria-posinset"><code>aria-posinset</code></a> and <a class="property-reference" href="#aria-setsize"><code>aria-setsize</code></a> are not provided, or are specified as the empty string,
             user agents MUST compute them as follows:
           </p>
           <ul>