Just to clarify, these codes do NOT give any additional free time.

The ONLY things that they give are a friendship circlet to the new player and the old player gets (depending on time referred player subs for) a circlet, a 2 person chocobo and a one time use crystal that unlocks the ability to teleport for free to the nearest crystal to any newbie leaf icon player on their friends list (the referred player may get that crystal too, I don't recall).

In game items only, 0 subscription time is included.
Oops, I thought I read somewhere that it gave some free time...in that case, posted edited, thanks for clarifying!