What "3 / 10" on a list means
It's how many of the list's items have been bought, without saying which ones or by whom. Until the reveal date, or for good if there's none, that and a notification that something was bought are all the list's owner learns.

The count sits at the right end of the line under the list's name, with a progress bar below it. It goes up when someone marks an item purchased and down if they un-mark it.
It never points at an item. Which items were bought, and who bought them, stays hidden from the owner until each buyer's reveal date, and for good when a purchase has none.
People signed in who follow the list's owner see the count too. People who aren't signed in don't.
