Shopify pos automatic discount doesnt work

We have upgraded to Shopify PRO POS

We have turned on the automatic discount feature

I want to set a discount where the customer buys 3 items and gets 10% off those 3 items BUT if they buy 4, they only get the discount on the 3 , if they buy 6 they get the discount on the 6 but if they buy 7 they only get the discount on the 6 and so on

The discount only works on item 2 & 3 in the cart but it doesn’t discount item 1 in the cart, if i set it to buy 1 get 3 the customer has to buy 4 but again the discount isn’t applied to the first item

Surely it cannot be this difficult to set up a BUY 3 AND GET 10% OFF DISCOUNT ???

Then I tried setting the minimum purchase amount being of the cheaper item and setting a minimum of 3 but it doesn’t even work ?

Any ideas ?