HiMy total refund is $1646, but I received $1532. I would like to know the reason?

Did you choose to pay your TurboTax fees from your federal refund?    If so, remember those fees are deducted from the amount you get.

How can I see my TurboTax  fees? 

  https://ttlc.intuit.com/questions/2565973-how-do-i-review-my-fees-in-turbotax-online

Yes, there are several reasons your refund may not be the amount you thought you were going to get.

If you requested a refund advance, or asked that your fees be paid from your refund, the your fees will be deducted from your refund. 

If you owe the bank a debt, they may have taken it from the refund. You can contact TPG customer service, follow this link for more.

If you owe the IRS back taxes, they will take it from your refund. If that is the case, the IRS will send you a letter explaining exactly how much they took and where it was applied.

Second, if you owe certain state and federal debts, you may have had a Treasury Offset to pay the debt. Click here to  contact Treasury Offset if you think that may be the case.

If you made an easily verifiable mistake on your tax return like entering a figure wrong on your W-2, the IRS may have corrected it before sending you your refund. If that is the case the IRS will send you a letter explaining the change.