Thank you for bringing this to our attention.
Lines 365 - 372 of the order-update.php page:
<p>
<label for="" class="readonly-bottom">Shipping:</label>
$<?php echo(number_format($row_WADAorders['OrderTax'],2)); ?>
</p>
<p>
<label for="" class="readonly-bottom">Tax:</label>
$<?php echo(number_format($row_WADAorders['OrderShipping'],2)); ?>
</p>
should be:
<p>
<label for="" class="readonly-bottom">Shipping:</label>
$<?php echo(number_format($row_WADAorders['OrderShipping'],2)); ?>
</p>
<p>
<label for="" class="readonly-bottom">Tax:</label>
$<?php echo(number_format($row_WADAorders['OrderTax'],2)); ?>
</p>