I think you're confusing the dividend payment of $1.27 with the attached value of the franking credits ($74.3m/136m shares = $0.54). For the $74.3m in franking credits to be paid out in full it requires a dividend of $173.5m, and not that the franking credits themselves are worth $173.5m.
There will be additional franking credits generated under the current strategy but David's figure of $0.89 per share in franking accounts for this as the current balance is $0.54.
SDG Price at posting:
$2.37 Sentiment: Buy Disclosure: Held