Received refund from IRS (as IRS TREAS 310 TAX REF) was less than refund computed by TurboTax. Why the difference ?

Is it a "refund offset" ? It was only 1 week ago, so an explanation letter should arrive soon.
See these 2 URLs:
https://www.irs.gov/Refunds/Tax-Season-Refund-Frequently-Asked-Questions
https://www.irs.gov/taxtopics/tc203.html