diff --git a/core-aam/index.html b/core-aam/index.html
index fa74f9282..1090cfcc1 100644
--- a/core-aam/index.html
+++ b/core-aam/index.html
@@ -9852,8 +9852,15 @@ <h3>Group Position</h3>
<a class="property-reference" href="#aria-level"><code>aria-level</code></a
>, <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 all 1-based. When the [=ARIA/property=] is not present or is "0", it indicates the
- property is not computed or not supported. If any of these properties are specified by the author as either "0" or a negative number, [=user agents=] SHOULD use "1"
- instead.
+ property is not computed or not supported.
+ </p>
+ <p>
+ If the <a class="property-reference" href="#aria-level"><code>aria-level</code></a> or <a class="property-reference" href="#aria-posinset"><code>aria-posinset</code></a> properties are
+ specified by the author as either "0" or a negative number, [=user agents=] SHOULD use "1" instead.
+ </p>
+ <p>
+ If the <a class="property-reference" href="#aria-setsize"><code>aria-setsize</code></a> property is specified by the author as any non-empty 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>
@@ -9863,7 +9870,7 @@ <h3>Group Position</h3>
</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,
- user agents MUST compute them as follows:
+ or are specified as the empty string, user agents MUST compute them as follows:
</p>
<ul>
<li>
diff --git a/index.html b/index.html
index b887e641d..ed7d1dcd4 100644
--- a/index.html
+++ b/index.html
@@ -12904,10 +12904,10 @@ <h2>Definitions of States and Properties (all aria-* attributes)</h2>
<div class="property" id="aria-setsize">
<pdef>aria-setsize</pdef>
<div class="property-description">
- <p><a>Defines</a> the number of items in the current set of listitems or treeitems. Not required if all elements in the set are present in the <abbr title="Document Object Model">DOM</abbr>. See related <pref>aria-posinset</pref>.</p>
- <p>This [=ARIA/property=] is marked on the members of a set, not the container element that collects the members of the set. To orient the user by saying an element is "item X out of Y," the <a>assistive technologies</a> would use X equal to the <pref>aria-posinset</pref> <a>attribute</a> and Y equal to the <code>aria-setsize</code> attribute.</p>
+ <p><a>Defines</a> the number of items in the current set of items, such as listitems, treeitems, options, comments, etc. Not required if all elements in the set are present in the <abbr title="Document Object Model">DOM</abbr>. See related <pref>aria-posinset</pref>.</p>
+ <p>This [=ARIA/property=] is marked on the members of a set, not the container element that collects the members of the set. To orient the user by saying an element is "item X out of Y" or similar, the <a>assistive technologies</a> would use X equal to the <pref>aria-posinset</pref> <a>attribute</a> and Y equal to the <code>aria-setsize</code> attribute.</p>
<p>If all items up to the current item in a set are present in the document structure, it is not necessary to set this <a>attribute</a>, as the <a>user agent</a> can automatically calculate the position for these items. However, if all previous items in the set are not present in the document structure at a given moment, the author MUST set this <a>attribute</a>to provide an explicit indication of an element's position.</p>
- <p>When specifying <code>aria-setsize</code>, authors MUST set the value to an integer equal to the number of items in the set. If the total number of items is unknown, authors SHOULD set the value of <code>aria-setsize</code> to <code>-1</code>.</p>
+ <p>When specifying <code>aria-setsize</code>, authors MUST set the value to an integer equal to the number of items in the set. If the total number of items is unknown (indeterminate), and the DOM is currently incomplete such that user agents would not be able to compute the correct number of items in a set, authors SHOULD set the value of <code>aria-setsize</code> to a <code>-1</code>.</p>
<p>When specifying <code>aria-setsize</code> on a <rref>menuitem</rref>, <rref>menuitemcheckbox</rref>, or <rref>menuitemradio</rref>, authors SHOULD set the value of <code>aria-setsize</code> based on the total number of items in the <rref>menu</rref>, excluding any separators.</p>
<p>The following example shows items 5 through 8 in a set of 16.</p>
<pre class="example highlight"><h2 id="label_fruit"> Available Fruit </h2>