The first part of the code already lists manufacturers
Code:
{if $manufacturers_menu ne ''}
{capture name=menu}
<form name="form_manuf" method="get" action="manufacturers.php">
<select size="12" name="manufacturerid" onchange="document.form_manuf.submit()">
{section name=mid loop=$manufacturers_menu}
<option value="{$manufacturers_menu[mid].manufacturerid}">{$manufacturers_menu[mid].manufacturer|truncate:18:"...":true}</option>
{/section}
</select>
</form>
{/capture}
{include file="customer/menu_dialog.tpl" title=$lng.lbl_manufacturers content=$smarty.capture.menu additional_class="menu-manufacturers"}
{/if}
You need to edit that part not adding an additional one
Code:
{if $manufacturers_menu ne ''}
{capture name=menu}
<form name="form_manuf" method="get" action="manufacturers.php">
<select size="12" name="manufacturerid" onchange="document.form_manuf.submit()">
{section name=mid loop=$manufacturers_menu}
{if $manufacturers_menu[mid].order_by lt 300}
<option value="{$manufacturers_menu[mid].manufacturerid}">{$manufacturers_menu[mid].manufacturer|truncate:18:"...":true}</option>
{/if}
{/section}
</select>
</form>
{/capture}
{include file="customer/menu_dialog.tpl" title=$lng.lbl_manufacturers content=$smarty.capture.menu additional_class="menu-manufacturers"}
{/if}