Yeah, but those calculations just show that the voltage and current measurements mean his 3.9 Ω resistor is probably closer to 4 Ω.
I'd suggest the calculations should be done using current vs voltage drop, not the measured voltage at the resistor, to see how that relates to wire resistance.
3.0 - 2.36 = 0.64 V and 0.64 V / 0.59 A = 1.08 Ω
4.0 - 3.11 = 0.89 V and 0.89 V / 0.785 A = 1.13 Ω
5.0 - 4.05 = 0.95 V and 0.95 V / 1.02 A = 0.93 Ω
So roughly 1 ohm total, or 0.5 ohm in each lead, giving approx one volt drop per amp. That matches what I've seen several times with low quality test leads, typically banana to croc clip.
Of course without the suggested measurements of output directly at the Korad, we don't know the exact voltage drop and I'm just assuming the Korad output is close to the setting.