I just poured a 2'x2'x32' piece of concrete for an automatic gate for a towing business. I was wanting a high psi pour. I poured a 6.5 bag mix with fiber mesh with 2 pieces of 1/2 (#4) rebar down the middle. I am trying to accommodate any big wreckers that may enter the yard.
What psi do you think we have?

Depending on your area and the type of aggregates used as well as the gradation of those materials is very important factor, as well as the water/cement ratio. The easiest way to tell would have been to take cylinders during the pour. Tough to guess at something like this with knowing so few variables. If they didn't over indulge in the water when pouring it, and the materials are all approved, you shouldn't have too many worries.