There are two numbering systems for Fringe episodes being used right now, depending on where you look - the actual script production number, and the order that they were aired during this season.
Jacksonville is episode #214, according to the
official Fringe press releases. That's the numbering system we use.
Jacksonville was also the 15th episode shown during Season 2. So you may see other places have the designation of Season 2 Episode 15, 2.15, or 2x15.
The
reason for the discrepancy is that the 10th episode shown this season,
Unearthed, was actually filmed during season one (which explains why Charlie was still alive) and shown as a "bonus" episode this season. That episode is officially #121, but since it aired this season, some people are counting it as a season two episode and calling it 2.10.
I know it's a little confusing, but I wouldn't really worry about the episode numbers so much - that's just a technical issue that unfortunately won't resolve itself until next season.
And that's probably more than you ever wanted to know about Fringe episode numbers.