Just to clarify,
For all but 4 items, you want to charge a flat rate shipping of 8
For 3 of the 4 items, you want to charge flat rate shipping of 3.50
so if they order 1 regular item and 1 of the other 3 items, they should be charged 11.50?
same as if they order 4 regular items and 2 of the other 3 items, they would still be charged 11.50?
For the forth item, you want to charge a flat rate of 8 only when 12 or more are ordered?
This is on top of the other flat rate charges? so 1 regular item, 1 of the other 3 itmes and 12 of the 4th item would be 19.50?
As for the rule being messed up, its difficult to say what the problem could be with out knowing what the rule is. would need details on how the rule is configured to be able to guess at why it would be garbled on reinspection.
