proc fastclus output interpretation

#1
Hello,

I am using proc fastclus to perform k-means clustering.

In Figure 42.2: Cluster Summary Table from the FASTCLUS Procedure, an R-square value is reported (please see link below).

https://documentation.sas.com/?docs...ttingstarted.htm&docsetVersion=15.1&locale=en

According to the documentation, this is the R-square value for predicting the variable from the cluster. Is this a result from fitting a linear regression model Variable_value=cluster?
Can someone explain this?

Thanks