How should a partially applied Customer Deposit show on a Customer Statement?

• Sales Order for 2 items, total £100
• Customer Deposit for £100 applied to Sales Order
• 1 item fulfilled, £50
• Sales Order Billed (£50)
• Other Item cancelled / closed

The remaining £50 from the Customer Deposit shows on the Customer record as Deposit Balance, but doesn't appear on the Statement.

I can't find any documentation on the fields available on the statement record. We already have some complex customisation on our Statement template to try and show Applied Transactions clearly:

<#list statement.lines as line>
                  <#if line_index==0>
                    <thead>
                        <tr>
                        <th style="width: 13%;">${line.datecol@label}</th>
                        <th style="width: 35%;">${line.description@label}</th>
                        <th style="width: 13%;" align="right">${line.charge@label}</th>
                        <th style="width: 13%;" align="right">${line.payment@label}</th>