Yith create discount first 6 with 70% keep the discount and the 7 other discount

My final customer need make a discounr rules with 1 to 3 with 70% discount and 4 to infinity 30%.

Example
Product price 100$
Qty 8

1 to 3 70% discount = 30*3 = 90$
4 to 8 30% discount = 70*5 = 350$

440$ final price.

I need to create a rule with this information.. i try with the intervals but if i set 8 the rules only take the higher