So exactly how many cards is frontier justice supposed to contain?

General
1

Coz I think I just received a retail pack rather than an individual expansion…

2

http://dtdb.co/en/set/FJ

Frontier justice contains 21 distinct cards and should have four of each card, for a total of 4x21=84 cards

Well, plus an extra 4x copies of Unprepared (errata).

Hope this helps!

3

Right! So, I’ve got 5 extra copies of frontier justice at no extra cost…

4

Plenty o’ goodies in them thar packs:

http://dtdb.co/en/set/FJ