The conditions for a future buyback is also stated in the shareholder letter dated 06/29/2018.
821 million $TGGI Common shares were already returned to the Transfer Agent and cancelled. That's documented in $TGGI's Quarterly reports.
Around 2.2 billon $TGGI Common shares are yet to be returned. There's no stated timetable for this.
What has happened, and what's yet to happen, is stated very clearly.
"... While $TGGI had 821 million shares returned to the Company last year, it is still committed to further reducing its share structure. The total number of shares $TGGI is seeking to reduce is still a total of 3 billion shares minus the 821 million already returned. $TGGI will not place a time table for the further reductions and will share with its shareholders as it has in the past when it retires shares. ..."
A future buyback can be one additional element $TGGI shareholders can look forward to.