Custom List Number Resets to 1 in Plate.js When Entering "5) A"

[koorukuroo]

Description

When trying to start a numbered list with a specific number other than 1 using Plate.js, such as entering "5) A", it automatically converts to "1. A", ignoring the initial number input.

Reproduction URL

No response

Reproduction steps

1. When entering items in a standard sequence, like:
   
   1) A
   2) B

the numbering proceeds as expected.

2. However, if I attempt to start the list with a custom number, such as:

   5) A
   

   the list automatically resets to "1. A", disregarding the "5)" input.

This seems to be an issue with the NumberedListPlugin, which defaults the list numbering to 1, even if a different number is specified initially.

Expected Behavior
When entering a list item with a specific starting number, such as "5) A", it should retain the custom number input (5), instead of automatically resetting to "1".

### Plate version

39.2.21

### Slate React version

0.103.0

### Screenshots

_No response_

### Logs

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### Browsers

_No response_