What did you use to create your define.xml?
Was it modern, user-friendly software that uses a GUI? If so, it would be very easy to find out and repair.
Otherwise, you can open your define.xml using e.g. NotePad++, search for the codelist, and if for “YEARS”, it both has def:ExtendedValue=Yes as well as an NCI code in the “Alias” child element (these are mutually exclusive), remove the def:ExtendedValue=Yes, at least if that is what you want.
Sometimes (but not always) it is easier to correct such things just using an editor, than trying for hours …
And … a good advice: take a Define-XML course if you want to learn to understand what you are doing.