Add field in orders details

Hello all. I want to add a field in order details in administrative part showing total amount of items or containing checkbox (that mean is item in stock or not. It should be between amount and tax price, see the image). How can i do that? I think that i need to add some new variables in “…/admin/views/orders/manage.tpl” or in “…/admin/views/orders/details.tpl” (probably the last is right cause it contains {hook name=“orders:items_list_row”}). But what variables i should enter?

Sorry if the question is silly, i am just starting to learn CS-Cart.