it differs by employer, I think. The W2s I can look at that were imported have 10 digits a space and 3 letters. The import should occur immediately after you enter the code. That would be an excessively long string to enter both lines. It may be easiest to enter the information yourself at this point, unfortunately.
Some employers provide an "Import Code" that may be in your name/address box or above the W2 information.
