Canon AT-1 Instructions Manual page 39

unfold the rewind crank and turn it in the
direction of the arrow on the rewind crank.
When the frame counter has reached the
"S"
mark, you should stop rewinding. Then pull
up the rewind knob to open the camera back
and lift the cartridge out.
If you stop rewinding the moment the
frame counter has reached the " S h a r k , the
film will not be completely rewound into the
cartridge and the film leader will still be
outside the cartridge.