Ref explains use of index card to measure 1st down

One of the most baffling scenes unfolded on a football field Sunday night when, in measuring whether the Dallas Cowboys attained a critical fourth-quarter first down, referee Gene Steratore produced an index card out of his pocket to aid in his determination.

The method and ruling left both sidelines perplexed and necessitated a postgame explanation from Steratore.

So Steratore didn't really need the use of the index card to make his call. It only reaffirmed what he had already known. How did it reaffirm it?

"My call was made based on my visual looking at the football and the front of the line and the pole."

Gotcha.