Why is the Rivo app miscalculating at checkout?

hello everyone.

installed a email/coupon app( rivo)

wen I’m testing it something not working wright:

when there is a listing that is discounted its says : “we have the best offer already” ( example of current offer : boy one for 120$ get the second for 60$ ) and the cod doesn’t effect the total amount , that’s great for me …

but when I’m adding a product to the cart that is not discounted its adding some 6-7% to the total amount ( 96$ for each product =192$ )

the price for the not discounted listing its wright