When you have created labels using the Mailing Label Report Wizard, what happens if you then want to use a different label size with the same generated names? There is no Mailing Label Expert and you cannot get back into the Mailing Label Report Wizard.
From Design View, go into the Section Expert or click Report – Section Expert. On the left hand side, click Details (not Details a, Details b, etc). At the right hand side you should then see a Layout tab. Change the label sizes from there and click OK.