edit the code for the quantity field:
<input type="text" name="eCartSurface_Quantity_<?php echo $eCartSurface->DisplayIndex; ?>" value="<?php echo $eCartSurface->DisplayInfo("Quantity"); ?>" />
<input type="text" name="eCartSurface_Quantity_<?php echo $eCartSurface->DisplayInfo("WAUID"); ?>" id="eCartSurface_Quantity_<?php echo $eCartSurface->DisplayInfo("WAUID"); ?>" value="<?php echo $eCartSurface->DisplayInfo("Quantity"); ?>" onkeypress="waec_showUpdate('eCartSurface_Update_Quantity_<?php echo $eCartSurface->DisplayInfo("WAUID"); ?>',this);" />
i have logged a big in our system so that the next update will generate the correct code.