There are TWO sets of Giant Gas Deals for the week of 4/20/14. The first set is buy 6 and get $.40 off per gallon, when you get 30 gallons of gas, it is $12.00 off. You can see the full Giant Gas Deals FAQ here.
The deals are calculated using the 30 gallons of gas, if you don’t fill up 30 gallons, you can calculate your deals here.