correct formulation

Author: vld-codra

plotpy/events.py

@@ -758,7 +758,7 @@ def get_zoom_param(
         Args:
             plot: instance of BasePlot to use as a reference.
             pos: position on the plot canvas of the current hotspot.
-            factor: factor by which to zoom (centered around 0).
+            factor: factor by which to zoom (zero-centered).
 
         Returns:
             Returns two tuples of four floats each, representing the parameters used