In using the TEI XSL to generate slides, it sensibly uses item/@n in any ordered list if present as the number for that item.
But what it doesn't do is carry on from a new number and number successive items sequentially:
<p> And some more chapters on a new slide:
<item n="13"> Names, Dates, People, and Places</item>
<item> Tables, Formulæ, and Graphics</item>
<item> Language Corpora</item>
The first item will be numbered 13, the second 2, the third 3, etc.
What I'm suggesting is that once the numbering has been changed, the default action should be to carry on from that number. I recognise that this means someone who wants to preserve erroneous numbering as printed '1, 2, 3, 3, 4, 6' would need to put in each number rather than just the second 3 and the 4. It just seems a more intuitive default to me the other way round.