Thanks Ernie for the response. The $5,914.50 is overstated Medicare wages still (in my mind at least). I have no way of knowing exactly what taxes were withheld that applied to the overpayment, because the overpayment was blended with my regular wages. Tri-Net (our benefits provider) refuses to refund anything, and the only thing they would do is provide me a corrected W-2c with a reduced Medicare wages and Medicare tax withheld amount, in an amount that doesn't make sense to me. I believe I'm being penalized for my employer's error.
Overpayment from my employer in 2020: $16,625 (before tax)
Amount I paid back in Feb '21: $10,555.64 (estimated net after tax amount I received)
Reduction in W-2c Medicare wages (corrected Box 5): -$10,710.95 (don't know where Tri-Net came up with this number)
Reduction in W-2c Medicare tax withheld (corrected Box 6): $-155.31
Still confused as to where to go from here.
