Yeah, I don't think that's a big deal that the tattoo wasn't "complete" after you saw it in Stranger in a Strange Land. It just means that Jack merely adds onto it after his initial tattoo and before the crash on the island.

It wouldn't make sense for the 5 to represent anything about the Oceanic 6 since he had to have gotten that tattoo before 815 crashed.

*Spoiler*

Besides all this, IMDB.com reports that those are Matthew Fox's real tattoos (the figures part of it at least).

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Abaddon