I typically have more than that on mine, and I've seen pics with more than mine, so I'd say it's on the low end. They can be quite bushy. How much you should be concerned is another question however.
Polyp extension will vary from tank to tank, many conditions contribute to the amount of PE a coral will have. Just because the PE isn't as great as it may be in another's tank, doesn't necessarily mean it's unhealthy.
The PE on mine is about 2x what ur pic shows. But as grim said Just because the PE isn't as great as it may be in another's tank, doesn't necessarily mean it's unhealthy.
if there is flow hitting it directly then it would have lesser PE ( typical of small tanks)
if the flow is more like FLOW then there will be more PE .. typical of bigger tanks