The first three generations of Paperwhites all have the same software. That would mean they all have 14 font sizes.
"Technically there are four different variations of Kindle Paperwhites. There are two versions of the second-gen Paperwhite, one with 2GB of onboard storage space and one with 4GB. The way to tell is to go to Settings > Menu > Device Info to view available space.
The software is essentially the exact same on all three generations of Paperwhites, so you aren’t going to be able to determine anything from a software standpoint."
https://blog.the-ebook-reader.com/20...rations-apart/
You might want to upgrade the software.