Canon AE-1 Instructions Manual page 12

Take several blank shots, releasing the shutter
and advancing the film, until the frame counter
reads "1" (the dot following zero) . While doing
this, keep an eye on the rewind knob. If it
rotates in the direction of the arrow, the film is
loaded correctly .
12
Each time you advance the film, the frame
counter also advances to the next frame . It can
count up to 38 frames. The numbers 20 and
36 are in orange to call your attention to the
fact that rolls with those numbers of frames
are or are almost finished .