They are two very different ways of measuring pressure. You may rest assured that the 3 tons was by the crusher system. While this number gives you a substantial working pressure, I'd still advise you to stay below 7,500 psi piezo, the value you will see in a loading table. Keeping the loads in the 24 gram -7/8 oz - 1 oz range, 1100 - 1150 fps, and low pressure will give you good performance and be kind to the gun and to the shooter.