The Mysteries of Paint

When I painted the first floor bathroom, which is really just a tiny powder room, I thought one quart of primer and one quart of paint would do the trick. Nope, I had to go buy another quart of paint and then another quart. Thus far taking me to just over a gallon of paint for this tiny room.

After having to run to Home Depot 3 different times, I thought I would solve this dilemma with the kitchen/dining room/solarium and just buy a gallon of primer and 2 gallons of paint. Now, it looks like we will only need 1/2 gallon of primer and one gallon of paint. I do not understand paint!

Does anyone need a gallon of orange paint for their house?