This patch *attempts* to actually implement what's described for the `Count`-entry in the PDF specification, see https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/PDF32000_2008.pdf#G11.2095911, which I mostly ignored back in PR 10890 since it seemed unnecessarily complicated[1].
Besides issue 12704, I've also tested a couple of other documents (e.g. the PDF specification) and these changes don't *seem* to break anything else; additional testing would be helpful though!
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[1] At the time, all PDF documents that I tested worked even with a very simple approach and I thus hoped that it'd would suffice.