Answer
Since the invalid value lives in the affected user's own personal profile record, you can't fix it by having that user open the settings screen themselves (it errors before they can). Instead, log in as a different user with the necessary admin access, open the affected user's Profile record from there, and correct the out-of-range value directly on it — with the affected user fully logged out while this happens. Once corrected at the profile level, the affected user can log back in and the previously-erroring screen opens normally.