Three dials, one result. Temperature declares what light you are claiming to shoot under, and the two shifts nudge the outcome off that declaration.
The part that trips almost everyone: a higher Kelvin number produces a warmer picture, not a cooler one. The number describes the light, not the output. Tell the camera the light is 8000K — very blue — and it compensates by adding amber, so the file comes out golden.
That is why Temperature and Shift A/B are really one amber–blue axis in two different units, and why a warm Kelvin paired with a B shift is not a contradiction. It is a broad warm base with part of it deliberately pulled back. The two dials are not equally fine across the range: a single 100K step is worth about 15 mired down at 2500K but only about 1 mired up at 9900K, so the shift is the finer control down at 2500K and the coarser one up at 9900K. On a low-Kelvin base it buys precision the Kelvin dial cannot give on its own.
Shift G/M is the second axis, and Kelvin never reaches it. It is the tint control: G cancels the green cast of fluorescent light and open shade, M goes the other way.