I got my nano too now and was thinking of the same. I took the thin outer edge of the dubble sided sticky sheet which you would normaly think is what you don’t want and throw away 
You get a hole for the battery and fits quite nicely and I don’t think it should cover everything on the back in case you want to remove the back plate sometimes later. The tab confused me too. Now I just don’t know what to do with the two big squares of the sticky sheet that is left