From where your stock journal is created? If from sales order -> delivery order ... then make sure that you have tax code on your sales order line (there will be tax section at the bottom of the sales order screen and tax amount will be shown also)... without tax your stock journal amount will be the same as sales amount.

If that doesn't help ... please give some more information as from where your are creating stock journal and what's your odoo version? and how is your tax set up.