quantity discount not counting/calculating properly

[mhu100]

I have a strange problem with the quantity discount.
1 item costs €3,95. By 2 items the price must be €3,50 and by 4 items € 3,00.
The problem is:
when I add 1 item to cart, the price in cart is €3,50 instead of €3,95.
when I add 2 items the price in cart is €6,00 instead of €7,00

Is there someone who knows this problem or even better anyone with a solution?

Thanks in advance