Wrong discount calculation

[vosco88]

I have a percentage discount set up when code is entered. When trying it out it has a weird behavior of calculating the percentage for the discount from already discounted total.

Example before applying the discount:

Total is 78 for which I would like to use 10% discount coupon.

After applying the discount

The applied discount should be 7.80. Which gets translated into subtotal price of 70.20. But then this is taken and used for the coupon discount of 7.02.

Also this order that a customer recently did

The sum of his products is 257, so the discount should be 25.7.
The subtotal in my view should be 257 and from that the discount should be subtracted to get to the correct amount of 231,30. It seems that the discount gets applied to subtotal and then from that subtotal it get calculated again ( wrongly as it is not the 23.13)

Can you help here?