If, at age 60, you withdraw from your 401K, and the taxes are removed before the money is dispersed, what line should the withdrawal be reported on to avoid a double tax?

I had such a withdrawal and reported it on line16b of last year's return.  I was looking over the return recently when I noted, what I feel is, the error.  I can see why most withdrawals would be reported on this line, but as I have already had taxes removed from my payment, placing the figure here would be taxing it a second time.  Yet, I don't know where else to put it in an adjusted return.