Why is my (in progress) refund amount changing when I log out and back in to TurboTax with no other changes being made to my income, expenses, or tax return information?

There was nearly a $1000 decrease in my return (in progress) estimate from the time I logged out the first time to when I logged back in to continue working on it. No changes were made. All that I did was logged out and back in a day later.