Reset page number with counter-reset

I think this – or something closely related – was tackled in https://gitlab.pagedmedia.org/tools/pagedjs/issues/74 and https://gitlab.pagedmedia.org/tools/pagedjs/issues/78, which were fixed in 1.29.0.

I'm having a similar/related problem, in that I can't reset page numbering to a given number. I may be doing something wrong, of course. If I understand correctly, this should reset the page numbering to start at 20:

p.page-20 {
    counter-reset: page 20;
}

Instead, this resets page numbering to 1, as if the rule is valid but the integer is having no effect.

HTML: counter-reset-page-integer.html

Result: counter-reset-page-integer-wrong.pdf

Expected result: counter-reset-page-integer-right.pdf