Haha, that ND Grad Filter thing is called a "Reverse Graduated Neutrel Density Filter" - so rather than the traditional light in the middle then getting darker toward the top edge. it is as its darkest in the middle and gets lighter toward the top edge. Its a filter to be specifically used when you have the sun at the horizon level or close to it. To counter balance the stronger light in that area
The desk is 70cm deep & 180cm long, it also weighs 80kg...its absolutely solid and I love it! To answer your inevitable next question its this one -
https://www.conforama.pt/secretaria-schema - who seemingly only have stores in Spain & PT so I am not sure if it will do you any good. However, I might be wrong, you would need to google around.
I am very very pleased with how the setup is coming together. I've just ordered a keyboard and will be ordering a mouse on Payday. Logitech MX Master 2S & K780 keyboard to compliment. Apart from some backlighting for the desk and monitor it'll be about done then!
Finally, I am beyond chuffed with the monitor arm. An excellent product, professional presentation, great build quallity, awesome cable management built into it. Totally recommend the brand