Total outstanding shares as of June 30, 2023 and 2022, were 94.9 million and 94.2 million, respectively. Under our stock repurchase program, during each of the three and six months ended June 30, 2023, we did not repurchase and retire any shares, and during each of the three and six months ended June 30, 2022, we repurchased and retired 2.7 million shares. For each of the six months ended June 30, 2023 and 2022, we acquired 0.3 million related to tax withholding for share-based compensation.

The calculation of basic earnings per share of common stock is based on the weighted-average number of shares of common stock outstanding in the year, or period, over which they were outstanding. Our calculation of diluted earnings per share of common stock assumes that any shares of common stock outstanding were increased by shares that would be issued upon exercise of those stock awards for which the average market price for the period exceeds the exercise price less the shares that could have been purchased by the Company with the related proceeds, including compensation expense measured but not yet recognized.

Our weighted-average number of shares outstanding for the three and six months ended June 30, 2023 and 2022 was as follows:


	Three months ended June 30,		Six Months Ended June 30,
(in millions)	2023	2022	2023	2022
Weighted-average number of shares of common stock outstanding - basic	95.4	96.2	95.1	96.2
Restricted stock units	0.9	1.2	1.6	1.8
Weighted-average shares and assumed conversions - diluted	96.3	97.4	96.7	98.0

Awards of potentially dilutive shares of common stock, which have exercise prices that were higher than the average market price during the period, are not included in the computation of dilutive earnings per share as their effect would have been anti-dilutive. For the three and six months ended June 30, 2023, the number of anti-dilutive shares was approximately 10.4 million and 9.5 million, respectively. For each of the three and six months ended June 30, 2022, the number of anti-dilutive shares was approximately 10.2 million and 9.0 million, respectively.