The Enigma machine worked reciprocally so that an identical machine with identical settings would, if fed the enciphered letters, show the deciphered letters on the lampboard. Hut 6 had Enigma replica machines that were logically identical to the machines that the Germans were using.
The Enigma machine was designed to be mirrored, meaning that an identical machine with identical settings would produce the same results when given the same encrypted message. Hut 6 had replicas of the German Enigma machines.