Typo error on pasport number

Hi everyone,
I realised after submitting my application that I entered my child’s passport number with one digit missing in the online form.

The application type is AN (registration), and added my child is under 18.

We already have a TLS biometrics appointment booked. The passport itself is correct and will be presented at biometrics.

Has anyone been in a similar situation? Was this treated as a minor typo and resolved at biometrics or by the caseworker, or did you need to withdraw and reapply?

Thanks in advance for sharing your experience.

Explain the mistake in a cover letter, upload it before the biometrics appointment, and explain there. It's only a typo, it should not be an issue.