We do not know why your refund changed since we cannot see your return or your screen. There is a "refund monitor" on your screen that changes as you enter data. You cannot take that monitor seriously until everything is entered. And many forms are not finalized. It is possible that some form that was not ready when you started entering data has now updated and affected the refund that you thought was the "right" one.
Before you file, it is a good idea to actually LOOK at your Form 1040 so you can see what is on it and see if it is accurate. Refunds are on line 20; tax due is on line 23.
https://ttlc.intuit.com/questions/1901539-how-do-i-preview-my-turbotax-online-return-before-filing