Container ListItems not working for Movie Set

I've been studying a few skins to try and learn how to extract basic movie set information for a given movie set. Looking at Estuary and @mikeSiLVO's Aeon Nox: SiLVO, I understand one method is to create a hidden container that will be populated with the contents of a set when that set is the listitem in one of your other lists.

I've made the list copying Aeon Nox's code ;D):

    <!--Hidden Set list-->

        <control type="list" id="4500">

            <include>HiddenControl</include>

            <content sortby="year" sortorder="ascending">videodb://movies/sets/$INFO[ListItem.DBID]/</content>

         </control>

But it's not working as I had expected. Container(4500).NumItems works correctly, but Container(4500).TotalWatched seems to be evaluating the number of sets watched rather than the number of items within a given set and Container(4500).ListItem(0).Year is just blank

I made some labels to test:

        <control type="label">

                <label>content path: $VAR[MovieSetsPath]</label>

                <textcolor>white</textcolor>

                <bottom>0</bottom>

                <font>GridUnfocused</font>

            </control>

            <control type="label">

                <label>NumItems: $INFO[Container(4500).NumItems]</label>

                <textcolor>white</textcolor>

                <bottom>50</bottom>

                <font>GridUnfocused</font>

            </control>

            <control type="label">

                <label>TotalWatched: $INFO[Container(4500).TotalWatched]</label>

                <textcolor>white</textcolor>

                <bottom>100</bottom>

                <font>GridUnfocused</font>

            </control>

            <control type="label">

                <label>ListItem(0).Year: $INFO[Container(4500).ListItem(0).Year]</label>

                <textcolor>white</textcolor>

                <bottom>150</bottom>

                <font>GridUnfocused</font>

            </control>

            <control type="label">

                <label>ListItem(-1).Year: $INFO[Container(4500).ListItem(-1).Year]</label>

                <textcolor>white</textcolor>

                <bottom>200</bottom>

                <font>GridUnfocused</font>

            </control>

But all I get is this: https://cl.ly/b7fe304b7177

 

Have I made a mistake somewhere?