STP = Standard Temperature and Pressure
C = Crankshaft
So, your STPTrq Clb-ft and STPPwr CHp are corrected crankshaft horsepower and torque.
Barometric pressure and ambient temperature will affect power output. Using a "corrected" figure attempts to normalize those effects. Typically, these numbed are corrected to 29.92 in hg and 60 F.