That means you used the current online program to file a 2018 return--and the current online software is ONLY for a 2019 return--no other year. So you used the wrong program.
What happened? Did you try to e-file? Or did you realize the mistake before you filed? Was it accepted or rejected? Let's hope it was rejected, because fixing your mistake will be easier.
What does it say for your e-file status?
https://turbotax.intuit.com/tax-tools/efile-status-lookup/