Use this expression to determine Inventory - Unsubmitted Orders
[=TN('{REPORT INVENTORY:[:MenuItemName]:Локальный склад}')-TN('{TICKET ORDER QUANTITY TOTAL EXP:(MN=[:MenuItemName]) && (OS.Status=New)}')]
There is need to add multiple constraints. You only need to check LESS THAN 1.
Real time inventory calculation is an expensive operation. Try to use it for items that is really needed. Better use product tags to enable it for specific items. For example there is no need to track it for water. Water inventory will never drop below zero in a serious restaurant.