Unless I’m missing something, it can’t be done to those exact specifications. The person who devised the assignment isn’t very good at math, or communicating. The spread you set up doesn’t meet the specs (you tried, but it’s not possible), and if I had to set content on a grid like that, I’d rather shut off the computer and go get a root canal I don’t need.
I tried to modify my post, but ran afoul of the edit-time allotment, so, here I’ll qualify my assertions:
You can, of course, set up a page with 7 columns, 2.5 mm gutters, and the trim, bleed, and margins shown. But then the grid-unit width and height listed just make a mess of it; neither the trim nor the margin dimensions given are evenly divisible by the grid so-called “module” dimensions.
Maybe someone will come along and teach us both how to satisfy that brief.
I just tried this myself. Not only are the instructions cryptic and poorly written, the numbers don’t add up.
I could go through it point by point to cite the mistakes, missing information, weirdly worded instructions, contradictions, and things that just plain don’t make sense, but that wouldn’t help you solve the problem since, considering the instructions, it isn’t doable.