How to dial ADF frequency in 0.5 kHz intervals?

  • I recently flew the NDB ILS DME Rwy 12 approach into Cardiff (EGFF), which is based on an NDB with a frequency of 388.5 kHz. The manual says:

    The frequency range is 190 to 1749.5 kHz, selectable at 0.5 kHz intervals.

    Unfortunately I could not figure out how to select that frequency on the ADF panel. The inner most knob changes the frequency in 1 kHz intervals. So how do I select that frequency?