O/S = Outstanding shares, shares issued and held by investors (including insiders)
A/S = Authorized shares, total number of shares that can be issued by the company. Usually issued as another source of liquidity for companies that have no cash to support operations, like GDTK.
A/S are increased or decreased by board resolution.
O/S are increased or decreased by buy back, splits, buy back and cancelation.
In GDTK: A/S = 39,990,000,000. O/S = 38.8B.
GLTA