When is a Snapshot completed, so I can start making changes to the VM?

When I take a snapshot in Fusion, a progress bar appears in the VM window, then disappears within seconds.

But, an image of a clock also appears over the Fusion icon in the dock. That clock takes a minute or two to disappear.

What process does the clock represent?  When is the taking of a snapshot completed?  When the progress bar disappears, or when the clock disappears?

Can I safely start making changes to the VM, that I want to be able to rollback, immediately after the progress bar disappears?

Or, is it safer to wait to make changes until the clock disappears?

Thanks

(The progress bar and the clock appear in my Fusion 3 which I'm still happily using... I don't know what appears in newer versions.)