Why is my deposited refund only $900 out of my $2080 return

TurboTax does not receive tax refunds and has no way to withhold any refund amounts.  If you chose to have your TurboTax fees paid from your refund, you authorized the IRS to send your refund to a bank, they deduct the amount of the fees you authorized, and no more.  They then forward the remaining refund to you.  If your expected refund was $2,080 and you only recieved $900, then the IRS adjusted your refund.  There are several reason why this may have happened. 

You could have made an error on your tax return such as a data entry.  Or you may have not reported something that was reported to the IRS, such as 1099-NEC, for which they adjusted your return and refund. 

Offsets - If you owe money because of certain delinquent debts, the IRS or the Department of Treasury's Financial Management Service (FMS), which issues IRS tax refunds, can offset or reduce your federal tax refund or withhold the entire amount to satisfy the debt.

If you owe federal or state income taxes your refund will be offset to pay those taxes. If you had other debt such as child support or student loan debt that was submitted for offset, FMS will take as much of your refund as is needed to pay off the debt, and send it to the agency authorized to collect the debt. Any portion of your refund remaining after an offset will be refunded to you.

the IRS should send you a notice as to why your refund changed. or you may be able to view a transcript of your return as revised using the IRS website.

https://www.irs.gov/individuals/get-transcript