Wait for the letter of explanation to come for the answer to your question.  Or have him log into his online IRS account  and/or use the Where's My Refund?  tool.    My guess would be they reduced your refund but then also added some interest payment for the delay in the processing time ... so it may be a combination of things.  

https://www.irs.gov/refunds

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

IRS has delayed processing of millions of returns.

When your tax refund is delayed, IRS pays you interest.

The extra dollars and cents are your interest, which is taxable interest income.

@toshajacks 

The son's refund is missing money, so it's not interest paid by the IRS.

@toshajacks - okay crazier things occur... please go back to his tax return and re-confirm the expected refund was $945.... any chance it was $935 and then the interest got tacked on?????

also, since this was paper filed, when was it filed?  many of us who post frequently on these boards are trying to understand how backlogged the IRS is with paper returns (and since they broadly process in the order received),  knowing when you mailed the return will help us set expectations with others. 

If the IRS sent a refund with "cents" included then it must be related to interest added for some reason.   But no one at TurboTax will know what the IRS did or why.   TurboTax gets no information from the IRS after you file your return.   The IRS will send a letter of explanation.   If you want to  call the IRS and sit on hold for a long time over a few dollars and change you can try doing that.   Only the IRS can explain the refund amount.

To call the IRS:IRS:  800-829-1040  hours 7 AM - 7 PM local time Mon-Fri

Listen to each menu before making the selection.

First choose your language. Press 1 for English.

Then do NOT choose the first choice re: "Refund", or it will send you to an automated phone line.

Instead, press 2 for "personal income tax".

Then press 1 for "form, tax history, or payment".  

Then press 3 "for all other questions."

Then press 2 "for all other questions."  It should then transfer you to an agent.

IRS can reduce your expected refund, yet still pay you interest on the reduced amount.

If you get a check from US Treasury, the interest amount is printed on it.