I found the tool somewhat confusing on first inspection, no documentation being supplied with it. On the other hand, it is intended for professionals who should not NEED documentation so, applying grey cells, the correct pins were selected and fitted ( there are 4 sets ) and the back was off in less than 10 seconds.
In the past , I have taken family watches to jewelers etc. to have batteries replaced. Now I can do it myself. The cost of the tool plus that of the battery was less than I would have had to pay to have the job done professionally. I am very happy with my purchase....