Pressure Altitude. 6000 MSL. altitude increases. 29.92. 5000 MSL. pressure decreases. 28.92.
On a standard day (29.92 & 15 Degrees Celsius), an altimeter set at 29.92 will show 5000 MSL if the field is at 5000 MSL. If the pressure drops to 28.92, the altimeter will still be at 29.92, but will show 6000 MSL. So Pressure Altitude (29.92) is 6000 MSL, and the aircraft will perfom as if it were at 6000 MSL. Then adjust Pressure Altitude for non-standard temperature to arrive at Density Altitude. Finally, set the altimeter to the local sea-level pressure of 28.92 to indicate the correct 5000 MSL altitude.