You cannot reset the admin password via the touchscreen. You must use Method 1 (Reset All Data) or, if that is locked out, use the "Trouble Reset" sequence:
A factory reset (also called initializing the machine) on the Konica Minolta bizhub C258 restores system settings to defaults, clears user data, and can resolve configuration errors or prepare the device for transfer. Factory resets vary by scope (partial settings reset vs. full initialization) and typically require administrative/service access. Proceed with caution: a full reset will erase address books, network settings, print/fax/scan logs, user accounts, and potentially stored documents. konica minolta bizhub c258 factory reset
If you're still having trouble, consider reaching out to Konica Minolta support or a professional technician for assistance. You cannot reset the admin password via the touchscreen