Why is Coupon taking MORE than it should? Example provided.

[Jeff_Mash]

1.5.8a - Why is the ot_coupon not calculating this correctly?

Example: I have a 20% off coupon with restrictions: Only allow discount on product from Category A.

I added that product to my order along with an indifferent item from Category B.

The Problem: The 20% discount being taken off is MORE than 20% when used with multiple items.

This screenshot should help:

And here is my Coupon Settings which appear to be correct (allowing the 20% discount to only apply to items in that category):

And here are the settings for the ot_coupon, where I don't have it calculating tax or shipping:

At first, I thought it might be related to Sales Tax (thinking that the coupon was somehow calculating tax). However, it doesn't seem to be related to tax, because I reproduced it on an order without tax.

Check out this example:

As you can see, it works fine with the one item (which qualifies for the discount). But when I add a second item which isn't part of the discount category, the 20% value isn't calculated correctly.

Can anyone help explain why those two problems are happening?

[lat9]

Just to 'weed out' other interactions, what happens if you disable "Reward Points"?