Hi,
Unfortunate, the "OFF" needs to be translated manually.
open this PHP file:
/templates/flexible_lightmart/html/com_virtuemart/productdetails/default.php
and search for "OFF" (use CTRL+F), and translate it as you wish.
Do the same thing for other pages.
Category Page: /templates/flexible_lightmart/html/com_virtuemart/category/default.php
Shopping Cart Page: /templates/flexible_lightmart/html/com_virtuemart/cart/default.php
Regards