[firekat]

Close enough. FL380 just means Flight Level 380 which is 38,000 feet above sea level - approximately. Flight Levels are predicated on an altimeter setting of 29.92 inches or 1013.2 mb. This is set at a specific alititude that is predicated on adjusted Mean Sea Level. All aircraft flying above this altitude will have their altimeters set to the same value (29.92 or 1013.2). This gives a standard reference point for aircraft to fly specific altitudes to maintain vertical seperation. There are some more fine points to all the altimetry of it, but it is roughly about that high above sea level give or take a as much as a couple 1000 feet or so depending on extremes in meteorological conditions.

The .84M is the percentage of the speed of sound in Mach.

The -47C is -47 degrees Celsius. At that altitude "standard temperature" or what we refer to as "ISA" is approximately -57C so the deviation is +10, much warmer than standard.