The Rec. Period value on the Auto Bank Reconciliation window, if displayed incorrectly, is a cosmetic issue and has not used in the reconciliation process. Closing and reopening the window will display the correct value.
The Rec. Period will be the period that the entered date falls into. This can be checked in the Ledger defaults:
Navigate to the System tab
Select Options then System Control Options
The information can be found in the Ledger Defaults tab.