If you open up the cost to complete window and shut it, the system thinks you have done a cost to complete and it puts the orange symbol against that line in the budget as the balance figure is showing in the cost to complete.
If you want to clear it, reopen the cost to complete, delete the line and save.
Then go back into the cost to complete and this time select the "Cancel" button. You will be back where you started.
If you are just checking the Cost to Complete you need to select "Cancel" rather than closing the window.