Consumption meters

I saw in the video that you had two different units that you were wiring in and in speaking within phase prior to getting a hold of this video they said I needed to have a dual unit or dual consumption meter but when I saw you install it installed only the one plus the link to Amazon only had one on there as well so I wanted to double check do I need to buy two or just the one and if I use your link do I just enter quantity of two if I need two of them I know that sounds like a dumb question but still a question I appreciate your time and thanks a lot