6 millimeters over 3008 pixels/23.7mm which makes this about 4x magnification.
Nikon 28-200 at 200mm closest focus, reversed and attached with a step up ring and tape on the front of a 70-200 f/2.8 with 2x teleconverter focused to infinity (closest focus vignettes). 16-inch long rig & it focuses at about 1/2 inch. The 28-200 needed to have the aperture taped open. I probably would get much better results with a 50mm f/1.8. All were shot at ISO 200 between 1/60 & 1/100 f/5.6 to f/16 on the long lens, wide open at f/5.6 on the smaller one.
Compare this jerry rigged contraption on the 28-200
Compare this with teleconverter & closeup diopter on the 70-200