This method of identifying visitors across devices is no longer recommended. Please refer to the Adobe Experience Cloud Device Co-op Documentation .
Analytics counts a visit each time a server call occurs with a Visit Page Number equal to 1.
If you look at the previous table , this occurred 4 times: at hits 1, 9, 11, and 12. Similar to visitors, this value returns to normal after the initial association because the Visit Page Number is reset back to 1 due to a change in the effective visitor ID.