If it is known, it's not one I've noticed before.  I just copied your text into Notepad, and looking back at my NVDA log, as I down arrowed through the text, for each line, it took between 17 and 19ms between recording the keypress in the log, and recording that it was reading the line aloud.  When I read with NVDA+down arrow, it read the whole text and I didn't detect a pause before that particular line either.

If you could set your NVDA log to debug, reproduce the issue and send me a copy of the log, I'd be happy to look into it for you.

Otherwise, I can only think of the usual troubleshooting suggestions:

- Try disabling add-ons (and if that helps, ensure you have the latest versions for all your add-ons, and try enabling them one at a time to see where the slowdown is coming from)

- Try a different synthesizer

- Do you have any speech dictionary entries or pronunciation entries which might affect numbers?

Does it only happen when the number is specifically at the end of the line?  EG does:

Order number 4977509 has been sent

exhibit the behaviour as well, or only

Order number 4977509

Regards

Quentin.