Kilometers (K) and Metres (M) 

It might be possible that K mean Kilometers and M refers to Meters in-game but they are DEFINATELY not to scale with the current measuing system on Earth.

To argue that the game is "unrealistic" because distances between planets are "only" 20km is ludicrious. Marathon runners RUN 20kim all the time on Earth!

The official website stated planet Mahattan as 12,000+ km in diameter is also definately refering to km as another unit of measurement differing form kilometers. America alone is 9 million km squared in Area!

Bottom line:
K,M,km in-game do not refer to actual "kilometers" or "meters" we used right now.