updated precision from 1 foot to 2 feet

Author: Andrew Leung

draft/core/geospatial-indexes.txt

@@ -106,7 +106,7 @@ bits and precision, see the :ref:`geohash <geospatial-geohash>` section.
 By default, geospatial indexes in MongoDB have 26 bits of precision
 and supports as many as 32 bits of precision. With 26 bits of
 precision, using the default range of -180 to 180, your precision
-would be about 1 foot or 30 centimeters. 
+would be about 2 feet or about 60 centimeters. 
 
 You can set the precision of a geospatial index during creation by
 specifying the ``bits`` option to the :func:`ensureIndex()