Pending Internal Review means just that, they're having someone look at it with real eyeballs to see what needs to be credited because the computer didn't do it automatically.

I had about 15k miles Pending for the last two weeks as I waited for some kenya Airways flights to post. They showed up yesterday, I'm hoping that's not how long it will usually take! (though I was happy to learn about a 500 mile bonus for each segment flown on Kenya Air!)