Assuming you have 4 lists, i.e. L1 Region, L2 Sub Region, L3 Sub sub Region, L4 Country, and they are all connected via 'Parent Hierarchy', such that:
Parent hierarchy of L4 is L3;
Parent hierarchy of L3 is L2;
Parent hierarchy of L2 is L1.
Then in your module that has Product, L4 Country and Month, you need not do anything more, because Anaplan automatically aggregate the values from multiple L4 to the same L3 parent; and from multiple L3 to the same L2 parent, and multiple L2 to the same L1 parent.