"Lüderitzland", today part of the "Sperrgebiet", was far bigger than Frederiks had thought.The contract specified its width as "twintig geograph'sche mylen" (20 geographical miles), a term that the tribal chief was not familiar with; 1 German geographical mile equals 4 arcminutes (7.4 kilometers), whereas the common mile in the territory was the English mile, 1.6 kilometers.