diff --git a/templates/books_for_series.html b/templates/books_for_series.html
index 286e90d..451b0fe 100644
--- a/templates/books_for_series.html
+++ b/templates/books_for_series.html
@@ -3,7 +3,6 @@
 			<tr class="thead-light"><th>Title</th><th>Book Number</th></tr>
 		</thead>
 		<tbody>
-		{% set last = namespace(val=0) %}
 		{% for book in books %}
 		<tr>
 			<td id="{{book.id}}">
@@ -30,10 +29,14 @@
 			</td>
 			{% set num = SeriesBookNum( series.id, book.id ) %}
 			{% if num == None %}
-				{# okay, if this is a parent book, the num == None, so make it use last real-book and add .01 to it to make sure it sorts just after the last one #}
-				<td data-sort="{{series.id}}.{{"{:02d}1".format( last.val )}}">
+				{# okay, if this is a parent book, the num == None, so find first child / sub_book's book number in the series #}
+				{# then we treat each book_num as a 0-leading 3 digit number - for the parent book we minus 1 from it #}
+				{% set tmp = SeriesBookNum( series.id, book.child_ref[0].sub_book_id ) %}
+				{% set num = "{:02d}0".format( tmp ) %}
+				{% set num = num|int - 1 %}
+				<td data-sort="{{series.id}}{{"{:03d}".format( num )}}">
 			{% else %}
-				<td data-sort="{{series.id}}.{{"{:02d}".format( num )}}">
+				<td data-sort="{{series.id}}{{"{:02d}0".format( num )}}">
 			{% endif %}
 			{% for s in book.series %}
 				{% if not book.child_ref|length %}
@@ -57,7 +60,6 @@
 						{% endif %}
 					</script>
 				{% endif %}
-				{% set last.val = num %}
 			{% endfor %}
 			</td>
 		</tr>