I can't see the details on your label, but I've never seen one that listed the kill date (pack date), that information is typically on the cases themselves. For wet aging a brisket you need the kill date and here is why.... Beef in the walk in cooler can be held a pretty long time since they might be 31° or so. Once they move meat from the cooler to the meat case, a label is printed and the sell-by or use-by date is calculated. The store is assuming your home fridge is ~40° and beef won't hold very long at that temp, so the use-by date is 4 or 5 days out. Here is where the gray area comes into play... It's possible a case of brisket has a kill date of 14 days ago depending on how fast they are selling. You might not want to add another 45 days to that especially if your aging fridge is 35° or higher. Or, it's possible the brisket came from a newer case and only has 5 or 6 days of aging on it.
Once I tell them I'm wet aging a brisket, my Sam's Club will tell me the kill dates on the cases stored in the walk in, and then let me choose from those. Then they take them in back and print labels. One summer we were buying a case of brisket and two cases of butts. They actually wet aged the full case for us, and I picked it up with about 30 days of age on it.