Resolving datacarpentry#320

Following @tajuakins suggestion and adding an instructor note.
the image below captures the effect of step 4 (in the ordered list of the lesson instructions), but I can also see the confusion because the Undo item is 2. in the image's list.
datacarpentry#320

Author: jas58

episodes/04-transforming-data.md

@@ -61,7 +61,7 @@ Both new columns will appear with green text, indicating they are numeric. The o
 It is common while exploring and cleaning a dataset to make a mistake or decide to change the order of the process you wish to conduct. OpenRefine provides `Undo` and `Redo` operations to roll back your changes.
 
 1. Click `Undo / Redo` in the left side of the screen. All the changes you have made will appear in the left-hand panel.
-  The current stage in the data processing is highlighted in blue (i.e. step 4. in the screenshot below). As you click
+  The current stage in the data processing is highlighted in blue (i.e. in the screenshot below). As you click
   on the different stages in the process, the step identified in blue will change and, far more importantly, the data
   will revert to that stage in the processing.
 
@@ -74,6 +74,10 @@ It is common while exploring and cleaning a dataset to make a mistake or decide
 
 4. Let's leave the dataset in the state before `scientificNames` was split.
 
+::::::::::::::::::::::::::::::::  instructor note
+The image captures the effect of step 4 (in the ordered list of the lesson instructions), but you can also see that the Undo item is "2." in the image's list.
+::::::::::::::::::::::::::::::::
+
 ## Trimming leading and trailing whitespace
 
 Words with spaces at the beginning or end are particularly hard for humans to identify from strings without these spaces (as we have seen with the `scientificName` column). However, blank spaces can make a big difference to computers, so we usually want to remove them.