Plain English Meaning
The distance-measuring radio is placed at the same spot as the glide slope antenna, which sits beside the runway near where aircraft touch down. So the DME tells you how far you are from the touchdown zone, not from the end of the runway.
Full Definition
An ILS configuration in which the Distance Measuring Equipment (DME) transponder is installed at the same site as the Glide Slope (GS) transmitter, located near the runway touchdown zone. In this arrangement, the DME provides slant-range distance from the touchdown area rather than from the runway threshold or the localizer antenna at the far end of the runway. Distance readouts on using this configuration the GS/DME site.