being serious ignore all recommendations, use them for guidance and no more, try gloves on, the fit is crucial, if your fingers are rammed to the tips the cold will get in. The glove must have a little looseness to allow for the insulation to trap some air. Also keep your body and arms warm, the body pulls blood from the extremities to keep the core warm, so if your core is cold your hands will be more so.
I am currently using some 3 year old treks that i don’t think are made anymore. they were fine down to -8 last winter.
Things i look for some insulation, yes i know it sounds obvious but you would be surprised with some “winter”gloves, a long insulated cuff (usually knitted and then a second cuff. I tuck the jersey between the two cuffs to prevent a cold spot where the veins are close to the surface.