Indicated airspeed, as sibling comments point out, is not true airspeed. The air is moving at 500 but the stagnation pressure is the same as if it were moving o

Indicated airspeed, as sibling comments point out, is not true airspeed. The air is moving at 500 but the stagnation pressure is the same as if it were moving only 300 at sea level so the indicated speed will be 300 +- calibration errors.