I am researching the Bombe Machine, having just completed a project on the Enigma Machine. I visited The Rutherford Journal - The Turing Bombe, and it claimed that
The scales on the three indicator drums are designed to show the ‘rotor core starting positions’ at a ‘stop’ when measured in terms of the corresponding Enigma ring-settings for the Enigma rotor settings: ZZZ. This is the reason why the letters on the scales on the indicator drums are in the reverse order to those on all the other drums.
I don't understand this explanation, though. Aren't the indicator drums used to determine the rotor core offset? And I thought that the rotor core offset was calculated by the rotor position minus the ring setting. As the Bombe tests the rotor positions from A to Z, shouldn't the indicator drums also run from A to Z, since the Ringstellung is assumed to be a constant ZZZ?