My iPhone 4 only shows 256 MB of RAM?
That is pretty bizarre. The iPhone 4 is supposed to have 2x256MB memory modules for a total of 512MB, but it sounds like, for some reason, your phone isn't seeing one of them. Your numbers bear this out too - the iPhone hardware sets aside 9MB of the total memory, resulting in the OS seeing 503MB or, in your case, 247MB.

Definitely take it in and try to exchange it or replace it.