Your gravel order is bigger than the hole you dug
A 12 by 20 pad at 4 inches of compacted base finishes at 2.96 cubic yards. That is not the number you order.
You buy loose yards, not finished yards
Material packs down. The calculator allows 15 percent for crusher run under a plate compactor.
2.96 finished yards times 1.15 is 3.41 loose cubic yards. That is what goes on the truck. Deeper lifts and clay subgrade take more than 15 percent, so check it before you order.
Tons move with the material
Same 3.41 yards, four different tickets.
Crusher run at 1.5 tons per yard comes to 5.11 tons. Clean #57 at 1.4 comes to 4.77. Sand at 1.35 comes to 4.60. Dry topsoil at 1.1 comes to 3.75.
Same hole, a ton and a half between the lightest and the heaviest. The densities on the page are defaults. Your pit has its own, and that is the one that belongs on your order.
Order it once
Put in your footprint, your finished depth, and your quarry's figures.