When it comes to ratings, there are countless ways to compare networks and broadcasts.

The Washington Post’s Lisa De Moraes reports Tuesday was “the first time [CNN] made a clean sweep of all the broadcast and cable networks on election night.”

As we reported yesterday, ABC was the top-rated network, and CNN was just behind the broadcast network in Total Viewers during prime time. So what’s the difference?

The category used by de Moraes is the Total Viewer average from 8pm-12:30am, which puts CNN ahead of ABC (and the other broadcast networks). But the problem with this way of breaking down the ratings is all the broadcast networks had local affiliate programming during this range, most from just after 11pm until 11:30pmET. This could certainly have contributed to ABC’s drop-off of 13,135,000 Total Viewers from 8-11pmET to 12,500,000 from 8pm-12:30amET.