Doubts in discount page

I added a aashirwaad atta product. I want to make a discount options based on qty, if customer purchase 1 number that discount should be 6% and if more than 3 numbers than the discount should be 10 % on each. Considering same i created two discount schemes for min 1 and min 3. While billing for 3 numbers, it is creating 2 items for billing. First one is getting 6% and the other 2 are getting 10% discount.please suggest on how to increase discount with qty.