Fixed `FactorRange`'s `start` property help string
``end`` --> ``start``
@@ -395,7 +395,7 @@ class FactorRange(Range):
The start of the range, in synthetic coordinates.
Synthetic coordinates are only computed in the browser, based on the
- factors and various padding properties. The value of ``end`` will only
+ factors and various padding properties. The value of ``start`` will only
be available in situations where bidirectional communication is
available (e.g. server, notebook).
""")
