Shipping

[TripShip]

For some reason when i use the suggested shipping rates from POPcustoms on my shopify store it is calculating a price that is much too high when shipping 2 different items but is calculating normally when shipping 2 of the same item. (ex: 2 shirts shipping at $12.50, but 1 shirt 1 legging shipping at $30) I am unsure how to correct this. It seems to be using both items "additional item" cost as well as both items base shipping cost whn shipping 2 different items.