How can I remove a traditional ira contribution that did not occur, for a previously filed return? I am trying to amend my 2018 return reporting $6500 but is $0.

I reported $6,500 as excess in 2018, then removed it within the required time period to avoid penalties, but it shows on the 8606 as total basis (which is incorrect since the total basis should be what would have carried over from the 2017 return line 14 totaling $3,474.  How do I correct the basis in the 2018 return?