Atypically, Yahoo appears to show a grossed-up dividend (i.e. the dividend, adjusted for franking credits) rather than the actual dividend paid to a shareholder.
As at 30 Apr 2018, Yahoo shows a dividend for Date 14 Feb 2018 of $2.8571.
Commonwealth Bank (CBA) actually paid a $2 dividend, fully franked. Australia's company tax rate is currently 30%. Therefore, the grossed-up dividend is $2 * franking rate/ (100%-30%) = 2 * 100% / (100%-30%) = 2*1/0.7 = $2.857142857
The Australian Taxation Office has a lot of information regarding franking credits/franked dividends: