Hi,
Thanks to create a new file in "templates/YOUR_TEMPLATE/html/com_hikshop/product/show_quantity_custom.php", put the code:
<?php
$i =$this->params->get('i');
$min_quantity =$this->params->get('min_quantity');
$max_quantity =$this->params->get('max_quantity');
$html =$this->params->get('html');
?>
<table>
<tr>
<td class="cust_qty">
<input id="hikashop_product_quantity_field_<?php echo $i; ?>" type="text" value="<?php echo JRequest::getInt('quantity',$min_quantity); ?>" class="hikashop_product_quantity_field" name="quantity" onchange="hikashopCheckQuantityChange('hikashop_product_quantity_field_<?php echo $i; ?>',<?php echo $max_quantity; ?>,<?php echo $min_quantity; ?>);" />
</td>
<td class="cust_plus">
<a id="hikashop_product_quantity_field_change_plus_<?php echo $i; ?>" class="hikashop_product_quantity_field_change_plus hikashop_product_quantity_field_change" href="#" onclick="return hikashopQuantityChange('hikashop_product_quantity_field_<?php echo $i; ?>',1,<?php echo $max_quantity; ?>,<?php echo $min_quantity; ?>);">+</a>
</td>
<td class="cust_minus">
<a id="hikashop_product_quantity_field_change_minus_<?php echo $i; ?>" class="hikashop_product_quantity_field_change_minus hikashop_product_quantity_field_change" href="#" onclick="return hikashopQuantityChange('hikashop_product_quantity_field_<?php echo $i; ?>',0,<?php echo $max_quantity; ?>,<?php echo $min_quantity; ?>);">–</a>
</td>
</tr>
<tr>
<td colspan="3" class="cust_button">
<?php echo $html; ?>
</td>
</tr>
</table>
inside and then in the HikaShop option "Quantity layout on product page" in Configuration > Display > Products, select the value "show_quantity_custom", this way you will have the desired layout, then you just have to customize it with some css properties.