Cluster is not updated after I add a new machine to the cluster

I added a new machine to the cluster, but then I checked again, and the cluster didn’t update the machine count and process count.

Can someone explain to me how it works?

By machine you mean an additional VM or physical server correct? Or do you mean you added an additional FDB processes? If the additional machine and their processes are not showing up you should ensure that they are running and if not take a look at the FDB trace logs to see if there are any errors (see: Understanding FoundationDB Log Files · apple/foundationdb Wiki · GitHub)