I believe you can achieve this by going into the NCM settings, and then down to the Configs link in the Configs section.
Then go down to the "Config Comparisons" section, and change the settings to "Display the number of lines"
I THINK this is how it is done... but I have been wrong more times than right...
I had set this up before we started doing the RTCD, but the RTCD emails look almost exactly like our comparisons do.
Perhaps there is another option within the job, or email action, that qualifies this...?
Please let me know if I was wrong, or really wrong...
-Will