在管理仪表板WooCommerce小部件中显示自定义净销售额

If you've Woocommerce installed and you check the WordPress Dashboard, you can see a widget from WooCommerce which shows you the order statuses and the total sale for the current month:

Because the net sales this month are my total sales in all and not my profit, I'm currently looking for a way to add a custom net sale under "net sales per month".

This net sales should be filled from a custom fee in each order which is named provision. So is this possible? If yes, how can I do this?