We can't tell you whether the IRS will give you part of your refund or take it all. They could determine that you could have all of it.
Tax Topic 151 means your return is under review. This can be done for various credit claims such as Earned Income Credit or any of the education tax breaks (this is not all inclusive). Your best bet it to wait until the IRS contacts you via letter which can take up to or more than 4 weeks for you to receive it.
They may simply need more information and nothing will be affected. In addition, they could potentially make changes which you can accept or contest the changes per the IRS letter.
