Answer:
They have too much caramel
Explanation:
The ratio to the perfect milkshake would be 5:3 (5 ice-cream, 3 caramel)
The ratio for freeze zones milkshakes are 10:7 (10 ice-cream, 7 caramel)
As you can see the amount of has ice-cream has doubled (5x2=10)
but the amount of caramel has increased more than double (double would be 3x2=6 but its not it is 7)
Therfore there is too much caramel for the 'perfect milkshake'
Hope this helps :)