Hi,

You can custom it via go to file:
– app/design/frontend/sns_riveshop/default/template/catalog/product/list.phtml for listing page
– app/design/frontend/sns_riveshop/default/template/sns/producttabs/items.phtml for module SNS Product Tabs
– app/design/frontend/sns_riveshop/default/template/sns/slider/default.phtml for module SNS Slider

Find and edit the bellow code:
echo "<span class='ico-product ico-sale'>-".floor(100-($finalPrice/$price)*100)." %</span>";