Based on Dick Johnson's test data, minimum sink (~ 100 ft/min)was at the lowest tested airspeed, just below 40 knots. Maximum glide was about 50:1 at around 55 knots, a plateau. A second plateau in the polar occurred between about 75 to 85 knots with a sink speed of around 250 ft/min. The best-fit quadratic equation fits the very low-speed and high-speed data well and goes through the middle of the second plateau, but over-estimates sink rate a bit in the low-speed plateau.

I wouldn't sweat the difference.