So, Mr. Khan & Mr. Magnum, a hypothethical:
You're cruising at FL310; actual SAT is -36°C (ISA +10°C), but the forecast SAT for FL350 (entered during pre-flight, with winds) is -64° (ISA -10°C). Are the Opt/Max altitudes & time/distance to Step-Climb figured on actual (-36° - 8° = -44°C extrapolated up to FL350), or entered/forecast (-66°C at FL350, extrapolated down, or in this case, extrapolated level)?
As Mr. Khan has implied, I'm rather dense, so please patronize me a little.