The Next and Go+Next show the name of the selected snapshot, and not the 'next' snapshot. The Prev and Go+Prev show the 'prev' snapshot.
I have an example with 3 snapshots:
1 is current 1 is selected:
1 is current 2 is selected:
2 is current 2 is selected:
2 is current 3 is selected:
3 is current 3 is selected:
As you can see, the Next-buttons show the same as the Go-button, while the Prev-buttons show the actual prev-snapshot.