Did you add the oil via the fill plug or through the shifter? If it was the latter, I've found it takes time for the oil to make its way down when pouring through the shifter. If so, your best bet would be to leave the fill plug out and wait until the oil stops coming out of the fill hole, then refit the fill plug. If you added the oil via the shifter and refit the fill plug as soon as any oil started to come out, and didn't allow some time for the oil to make its way down, I think you'll find it is overfull.