I updated rstan using update.packages(), with the repo set to: Global (CDN) - RStudio
The actual current RStan version at CRAN is 2.21.3. So rstan is up-to-date on Ubuntu. On my windows machine, after updating rstan, RStudio now lists rstan as version 2.26.2. Also, when I run PackageDescription, I also get version 2.26.2.
packageDescription("rstan")$Version
[1] "2.26.2"
When I went to the Description file in the rstan folder in the Windows library, it has the lines:
Package: rstan
Type: Package
Title: R Interface to Stan
Version: 2.26.2
The corresponding Version statement in the Ubuntu R library reads 2.21.3
That's what I am asking about. It may have been just a typo when someone created the Description file.