Whenever I have any misunderstandings with the financial side, I always contact calsavers customer service https://www.pissedconsumer.com/company/calsavers/customer-service.html . I am pleased with the speed of response and professionalism. They explain everything to me in detail, help me understand the payments and conditions. In addition, there is no intrusiveness, as in some other companies. If financial issues arise again, I will definitely contact them - everything is resolved quickly and without unnecessary problems.

I do not understand this either, but officially they state:
"Our annual subscription model ensures that our product for Android, Windows and Web benefits from a flexible infrastructure, offering you advanced benefits like Cross-Platform library sync while enabling us to keep improving the product. We’re always exploring new pricing models to better serve our customers."
Which can be found here: https://support.goodnotes.com/hc/en-us/articles/10359438511119-Goodnotes-for-Android-Windows-and-Web-Subscription-FAQs#h_01H9FVJ66ZDF4YM0MZKVR86RH8

However I'm displeased with a lack of options in this regard and their explanation. If it is due to the cross-platform support, than I would like an additional option to just buy a one time license for 2 options — Windows and Android, since the website has to be hosted by them, so it's understandable, that it can't be permanently owned.