Mobile had its first $2bn day in the US on Cyber Monday 2017

"Mobile had its first-ever $2bn shopping day in the US on Cyber Monday, helping drive online sales to its largest total in history of $6.59bn for the day.
According to Adobe estimates, smartphones alone accounted for $1.59bn of revenue on the day, representing an all-time high year-on-year (YoY) growth of 39.2 per cent. Smartphone traffic also saw growth of 22.2 per cent, helping overall web traffic to retail sites to increase by 11.9 per cent.
Overall mobile devices represented 47.4 per cent of retail site visits – 39.9 per cent smartphones, 7.6 per cent tablets – and 33.1 per cent of revenue – 24.1 per cent smartphone, nine per cent tablets. Mobile transactions were 12 per cent higher in value on average than Cyber Monday 2016."

Source:  Mobile Marketing, 29th November 2017

Note - so $1.6bn for mobile, and $0.6bn for tablets
Plus - Black Friday stats here
Plus - Data on in-store footfall here