Count rows that meet certain requirements and then subtract that number from another count

Let's say I have data like this:

And I want to count all the so called "Private Orders". They are boxes with an unique ordernumber and a Standard priority and UPS delivery. (There's 2 in this example, 6 and 7) Then I want to count all the boxes with Standard priority and subtract all the Private orders. (There's 9 boxes with Standard priority, minus the 2 Private orders = 7.)

Is that possible in Tableau? I want to display the number 7 in a textbox.

For Private orders use this field

IF 
{FIXED [Type], [Ordernumber] : COUNT([Ordernumber])} = 1
AND [Type] = 'Boxes' And [Priority] = 'Standard' And [DeliveryMethod] = 'UPS'
THEN 1 ELSE 0 END

For all boxes use this

Sum(
If [Type] = 'Boxes' And [Priority] = 'Standard' then 1 else 0 end
) 

SO FOR FINAL OUTPUT YOU MAY USE THIS DIRECTLY say calculation2

Sum(
If [Type] = 'BOXES' And [Priority] = 'Standard' then 1 else 0 END
) -
Sum(IF 
{FIXED [Type], [OrderNumber] : COUNT([OrderNumber])} = 1
AND [Type] = 'BOXES' And [Priority] = 'Standard' And [DeliveryMethod] = 'UPS'
THEN 1 ELSE 0 END)

For matching pattern change the above field to say calculation3

Sum(
If [Type] = 'BOXES' And [Priority] = 'Standard' then 1 else 0 END
) -
Sum(IF 
{FIXED [Type], [OrderNumber] : COUNT([OrderNumber])} = 1
AND [Type] = 'BOXES' And [Priority] = 'Standard' And REGEXP_MATCH([DeliveryMethod], "UPS")
THEN 1 ELSE 0 END)

the data used

Results