Modifying the special offer add on
 

Hi I need help modifying the special offer module

We have this special offer set up - Buy x get y where the user has to buy 4 products in total and we can select the categories the customer can buy from underneath (see image attached)
Now the customer can buy 4 products from one and nothing from other. there is an OR condition here Category 1 || Category 2

If we can change it to AND condition it will solve the problem. because then they have to buy the single product that is present in Category 1 to avail the offer

Where can I change the OR condition to AND therefore forcing the customer to buy from both categories.