Wrong numbering for extensions

[nus-pe-bot]

Note from the teaching team: This bug was reported during the Part II (Evaluating Documents) stage of the PE. You may reject this bug if it is not related to the quality of documentation.

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Steps to reproduce:

1. In the DG, scroll to use cases.
2. For the use case: add a contact

Expected:
I think for the extensions when the contact details are invalid, the numbering is wrong as the extension should happen right after user request to add a contact.

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_{[original: nus-cs2103-AY2324S2/pe-interim#3416] [original labels: severity.Medium type.DocumentationBug]}

[cyqjoseph]

Team's Response

No details provided by team.

Duplicate status (if any):

Duplicate of #5573