When you start the amend process, the refund that is shown in TurboTax is reset to zero. 

You will still get the original refund. The amended return will show the difference you owe, or that you will get back as a refund (in your case, in addition to the original refund amount).  

You can confirm this by printing your amendment and looking at the 1040X. On Line 18 you should find your original refund amount and on line 21 you should see your additional refund.  If you paid on your original return it will be on line 16.  If there is an amount owed with the amendment, it will be on line 20.