Once your return has been filed and accepted for processing, you can only change through the "amend" process -- tell turbotax that you want to amend a filed/ accepted return ( suggest wait till your current return has been processed). During the amendment process , you will see a form 1040-X being prepared-- this is a reconciliation and you can see if you owe more or the IRS owes you . But you have to do the amendment to find out and then decide if it is worthwhile.
Notre that since there is no personal exemption ( it is set to Zero for the years 2018 thru 2015 ), the only effect of being a dependent is in the limitation of standard deduction and thus on taxable income.
