How to tell Mac that my dual monitors are two separate monitors instead of one?

Hi everyone,

I'm trying to use dual external monitors with my Mac air WITHOUT using the screen on the Mac itself. I have a Mini DisplayPort to Dual HDMI adapter (j5create), and both of the external monitors are working while the Mac itself has the lid closed. Nearly mission accomplished.....

While setting the monitors up (when my Mac was open and the screen was being used), I had the option in system preferences --> displays to "arrange" the screens. I unchecked the mirror displays box and noticed that the only two "screens" being recognized by the Mac in the "arrange screens" window was the Mac air itself and what seems to be the combination of my two dual monitors.

When I close the Mac air, I don't even have the "arrange" option anymore. It's like my Mac thinks that these two external monitors are one, and I can't separate them.

Ideally, I want to be able to work on the two external monitors and not use the screen on the Mac at all. Could anyone provide suggestions? I've attached two screenshots of the display options when the lid of the Mac air is closed versus open. When the "arrange" option does appear (and Mac lid is opened), I click on the left screen and it's highlighting (in red) both of my external monitors.

When Mac lid is closed:

When Mac lid is open:

Here's some info about my air:

- Using macOS Sierra (Version 10.12.3)

- 13-inch, early 2015

Thanks,

Courtney