Minimum amount being applied to each line item

I have this module set up to calculate 7% of the order total with a $3.50 minimum.

It works well EXCEPT I've noticed that for orders that fall below the minimum threshold (i.e. where 7% of the cart total is less than $3.50) - the minimum amount is taken and multiplied for each line item in the cart - giving hugely inflated shipping costs. See below for an example:

If I have 5 items in my cart that are $5 each - the shipping amount is appearing as 5 x $3.50 ($25). It should be $3.50!!