Code 766 refers to a credit added onto your account, such a refundable tax credit or an overpayment applied. Do you know which items you were expecting a refund for?
It is impossible to say what the next transaction code will be; it depends on what happens with the processing of your return by the IRS. It could be, for example, code 570 for a delay in processing or code 846 for a refund issued.
See also: Taxpayer Advocate - Income Transcripts
