Prove the bank position
Confirm opening balance, imported statement continuity and every bank line's accounting outcome. The accounting bank balance and the statement balance must agree to zero difference for the reconciliation point.
What reconciliation protects
Once reconciled, the related bank position should not be casually deleted or changed. This protects the evidence used to prove the period and prevents a later edit from making a previously completed reconciliation unreliable.
If a genuine correction is needed
Use the authorised unreconcile/correction route, make the source correction, then reconcile again. Keep the reason and audit trail rather than deleting/reimporting activity to make the screen look clean.
If the difference is not zero
Find the first date the running balance diverges, then check opening balance, missing/duplicate statement lines, wrong dates, wrong bank account, settlement allocations and posted corrections. See Banking & reconciliation.