Concrete.... What did I do wrong?

I poured 5 runs that were 4' x 20'x 4" deep. It figures out real close to 1 yard and I used the cart. Each time they were supposed to be long yards. Also I had wire and plastic on top of my sand. I barely had enough each pour and that is not taking into account that the sand base made the thickness less than 4".

They might short you but it is not going to go over if you use the cart. I just had a foundation poured for a shop. It was 30'x40' with a 12'x40' lean to on the side. They brought 3 trucks and had a little left over which made me a nice ramp.