It's probably still acclimating to your tank. For the next few days, you can expect to see it expand and shrivel many times throughout the day until it get's 'happier". It almost looks like it may have a tiny bit of bleaching going on, but it is hard to tell when it's not fully expanded. If the tentacles are disporpotionately short when inflated, I would keep a close eye on it as many people feel this is a sign of starvation. Don't worry about trying to feed it right away though, let it settle in first. If you have clownfish and they are bugging it, you might try putting a strawberry basket over it to keep the clowns away for a while.
My first anemone scared the bajeebers out of me the first week or two I had it. The anemone was completely bleached and shrivelled up at least 6 times a day for awhile. And it was my first tank and it had only been up 2 months when I brought it home (yes, I know...a very stupid thing to do, but everyone makes mistakes). Two and a half years later, it's now a pretty green with a pinky-orange cast to it, has split well over a dozen times and sitting in a tank at my LFS waiting for me to get my new tank up and running!
Good luck with your anemone!
-Janel