I did adjust Cost Basis for only 1 line of the Stock Sales....for ESPP bargain element reported on 2017 W-2. If I report all 70 transactions, I will receive the message: Per IRS electronic filing specifications, returns with more than 25 other withholdings cannot be electronically filed. I would rather not do a paper return if possible.
I would do a "see attached" with a total for all withholding in that one line. Do a 2nd line for the one items with the adjustment.
Alternatively, since all withholding in from the one source, just do a total withholding on one of the 25. I often say to others "If they can't take a joke, ...." Others use CAGMC