As you are creating an epub, the page numbers are calculated by the device. See
https://wiki.mobileread.com/wiki/ADE#Page_numbers for how they are calculated. If the numbers match the original document, that is a fluke. I believe this method is common for all devices that use the Adobe SDK. The page number in the margin is the same and there is an option in the reader settings to turn it off.
If you want a per-screen page count on a Kobo device, you need to send the epub to the device a kepub. This will be read using a different renderer. To do this, you can use the
KoboTouchExtended driver.