I mixed mine 60/40 (coolant/water), since by mixing this ratio it brings the boiling temp up about 15 degrees. If you mix it 50/50 the coolant boils at like 254 degrees. I don't know what the dealer did, but when I first bought my car the coolant was so light pink, which had to much water. In the summer time I came to a light and I saw steam coming from under the Hood
a little bit, which was from the coolant boiling over through the overflow spout/hose. I changed the coolant, while mixing it 60/40 and never boiled over since.
On the back of the gallon it should give you different choices of ratio mixtures.