Registration says "invalid local phone number" after OS 10.3x restore

I have an old PowerBook G4 that's still in great shape and I wanted to restore it for some limited usage. The restore went without a hitch, but now OS X is prompting me to register the computer. When I enter my phone number, I get this pop-up window:

"The local phone number you entered is not valid.

Exchange number must be greater than 200, and cannot be 411, 611 or 911."

Any thoughts on this? I really don't need to register this computer as it will mainly be used for internet browsing.

I've already got an Apple ID for my newer Macs.

Any help to either bypass registration or correctly formatting the phone number would be appreciated, thanks!