GPO version numbers are an important part of the change-tracking process in any Active Directory environment, but are exponentially more useful in domains with multiple Domain Controllers. Any time that changes are made inside Active Directory, including any changes made inside Group Policy, Active Directory replicates those changes around the network to all Domain Controller servers. This replication process can take a few minutes, or a few hours, depending on the size and scope of your network and your DC configuration.

When you are making changes inside Group Policy and immediately testing those changes, you run the risk of pushing the changes to one Domain Controller, while your test client computer is pulling GPO information from a different DC. In this case, you certainly could not expect to have immediate results on that client workstation, because you have to wait for replication to finish before the new GPO information exists on all of the DCs.

All that is to say that checking these GPO version numbers across your multiple Domain Controllers can be a practice worthy of your time while troubleshooting potential synchronization problems. Your GPO version numbers should be the same among all DCs in the environment. If they are not, you are either still waiting for replication to finish, or something has gone wrong during the replication process and you now need to turn to Active Directory itself to figure out why.