@Angelyn_T
Please Learn from this input. There is no Need to Undo any reconciliations.
@ggoodman
Use Banking menu. This is either Write Check or Make Deposit, depending on the entry you want to make. The "expense" or "from" account is Equity. You stated this is Historic, so the entry should be dated, for instance, Dec 31 of your Prior year that you are working on right now. If you are working on 2018, date this Dec 31, 2017. That $50 from expense or income in a prior year rolled into Equity, already.
Now you can reconcile just fine.
