no do not enter the number in two places. they are for different purposes
dividend distribution paid from accumulated earning and profit (AE&P)- at one time you were a C Corporation and you have earnings that were not previously distributed to you as a taxable dividend. (report on M-2 column c) and your k-1 box 17.(possibly) but if you distribute AE&P the corp must issue the shareholder a 1099-DIV.
the default for distributions is first from S-Corp earnings , then PTET, then C-corp earnings, then other (tax exempt income). if there is AE&P, an election must be made if AE&P is to be distributed first.
on the other hand the distribution of S corp profits are not taxable unless they reduce your tax basis below zero (no 1099-DIV is issued). report on M-2 column a. these will also show on your k-1 box 16