Thank you Dan! I understand the confusion on these sets because they are rather confusing.
The Topps Attax Code cards -- the set we are talking about here -- was distributed in actual Topps Attax packs back in the day. In each pack you'd get a certain number of base cards, either a gold or silver foil card, and a code card. There were 30 of these code cards.
Then, in 2010 Topps Series 2, code cards comprised an insert set of 27 cards. Finally, in 2010 Update Topps created another 50 card set. Here are pictures of what each looks like:
Attax Code Cards -- Easily distinguishable from the others by looking at the top of the white code box. It has the words "Enter code and battle at toppstown.com"
Series 2 Code Cards -- Compared to the Attax code cards, the white box is smaller and doesn't have any text in it besides the code.
Update Code Cards -- The code box is the same size as the series 2 code boxes; however, the code text is smaller.
#COMMONCARDSMATTER
"The 0-2 pitch... SWING AND A MISS! Struck him out! The Philadelphia Phillies are 2008 World Champions of baseball!"
- RIP Harry Kalas