DOCS-246 change to oplog example

Author: Bob Grabar

source/core/replication.txt

@@ -300,9 +300,9 @@ Before oplog creation, you can specify the size of your oplog with the
 change the size of the oplog by using the :doc:`/tutorial/change-oplog-size` tutorial.
 
 In most cases, the default oplog size is sufficient. For example, if an
-oplog that is 5% of free disk space fills up in an hour, then
-secondaries can stop copying entries from the oplog for 20 hours before
-they require full resyncing. If this were the case, you would have a
+oplog that is 5% of free disk space fills up in 24 hours of operations, then
+secondaries can stop copying entries from the oplog for 24 hours before
+they require full resyncing. This example describes a
 very high-volume member. In many circumstances, the default oplog can
 hold days of operations.