The
Magnification Ratio control in the lower-left corner of a Composition,
Layer, or Footage panel shows and controls the current magnification.
By default, the magnification is set to fit the current size of
the panel. When you change magnification, you change the appearance
of the pixels in the panel that you are previewing, not the actual
resolution of the composition.
Note: After Effects renders vector
objects before zooming (scaling for preview), so some vector objects
may appear jagged when you zoom in on them. This does not affect
scaling of layers or rendering to final output.