You may get a popup/message when you save your perspective, saying that tagging updates exist that have not yet been reflected into group membership.  This means that the values of the existing tags have changed but have not been processed yet for the new groups in the perspective.

As an example, you have a perspective for Users like above.  A user has moved from the Accounting department to the IT department.  You change their user tag, in this case ch_user, from ACCT to IT.  In your perspective, you have an ACCT group for accounting users, and an IT group for IT users.  The above message will appear if the CloudHealth platform sees that tag change, but has not processed the change to move the asset (user) from one group to another. 

This message will disappear on its own once the CloudHealth platform has processed this change in the back end which can take up to 24 hours to complete.