A typical dryer here in the US can draw up to 20 amps at 240V, or 4,800 Watts. If you do this for an hour, it's 4.8 KWh (Kilowatts*hours). Our laundry gets done in about 40 minutes for a load. Your numbers do look off by a factor of 1000.

So if your dryer runs 800 Watts (at 220v) Each load takes about 2 hours and you processed four loads, this should be:

800w * 2 h / load * 4 loads = 6400 watt-hours or 6.4 kilowatt-hours (KWh). If your consumption varies from 400 to 800 watts, then the consumption of 5.987 KWh looks about right.

Here in the US we use commas to separate groups of three decimal places with commas and place decimal fractions behind the decimal point. My cousins in Germany do just the opposite. They use the periods to separate groups of three decimal places and the comma to separate the unit and the decimal fraction. Could it be the number was formatted 5,987 KWh for Europe?