debt issuance costs : debt issuance costs are reflected as a direct deduction of our long-term debt balance on the consolidated balance sheets . we incurred debt issuance costs of $ 15 million in 2018 and $ 53 million in 2016 . debt issuance costs in 2017 were insignificant . unamortized debt issuance costs were $ 115 million at december 29 , 2018 , $ 114 million at december 30 , 2017 , and $ 124 million at december 31 , 2016 . amortization of debt issuance costs was $ 16 million in 2018 , $ 16 million in 2017 , and $ 14 million in 2016 . debt premium : unamortized debt premiums are presented on the consolidated balance sheets as a direct addition to the carrying amount of debt . unamortized debt premium , net , was $ 430 million at december 29 , 2018 and $ 505 million at december 30 , 2017 . amortization of our debt premium , net , was $ 65 million in 2018 , $ 81 million in 2017 , and $ 88 million in 2016 . debt repayments : in july and august 2018 , we repaid $ 2.7 billion aggregate principal amount of senior notes that matured in the period . we funded these long-term debt repayments primarily with proceeds from the new notes issued in june 2018 . additionally , in june 2017 , we repaid $ 2.0 billion aggregate principal amount of senior notes that matured in the period . we funded these long-term debt repayments primarily with cash on hand and our commercial paper programs . fair value of debt : at december 29 , 2018 , the aggregate fair value of our total debt was $ 30.1 billion as compared with a carrying value of $ 31.2 billion . at december 30 , 2017 , the aggregate fair value of our total debt was $ 33.0 billion as compared with a carrying value of $ 31.5 billion . our short-term debt and commercial paper had carrying values that approximated their fair values at december 29 , 2018 and december 30 , 2017 . we determined the fair value of our long-term debt using level 2 inputs . fair values are generally estimated based on quoted market prices for identical or similar instruments . note 20 . capital stock preferred stock our second amended and restated certificate of incorporation authorizes the issuance of up to 920000 shares of preferred stock . on june 7 , 2016 , we redeemed all 80000 outstanding shares of our series a preferred stock for $ 8.3 billion . we funded this redemption primarily through the issuance of long-term debt in may 2016 , as well as other sources of liquidity , including our u.s . commercial paper program , u.s . securitization program , and cash on hand . in connection with the redemption , all series a preferred stock was canceled and automatically retired . common stock our second amended and restated certificate of incorporation authorizes the issuance of up to 5.0 billion shares of common stock . shares of common stock issued , in treasury , and outstanding were ( in millions of shares ) : shares issued treasury shares shares outstanding .

Table: shares issued treasury shares shares outstanding balance at january 3 2016 1214 2014 1214 exercise of stock options issuance of other stock awards and other 5 -2 ( 2 ) 3 balance at december 31 2016 1219 -2 ( 2 ) 1217 exercise of stock options issuance of other stock awards and other 2 2014 2 balance at december 30 2017 1221 -2 ( 2 ) 1219 exercise of stock options issuance of other stock awards and other 3 -2 ( 2 ) 1 balance at december 29 2018 1224 -4 ( 4 ) 1220

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Question: what is the net increase in outstanding shares during the period of 2016 to 2018 , in millions?
Answer: 6
Calculation: subtract(1220, 1214)