Hi, I would love some advice on our current plans. We have a tiny backyard that we're about to redo as part of a whole landscape re-design. Right now there's a giant concrete slab that pretty much covers the entire space but it's just not inviting and we never end up using the back yard for this reason. We got some designs and quotes to put a deck over part of it and fill in the rest with gravel to create more defined spaces (second desire was to make the deck to grade with our home flooring so you can walk out without steps). But I keep hearing the guidance that a deck should only be 20% of a space max, with 150 sq ft recommended or 300 sq ft max. This current deck design is about 500 sq ft. What do you think?

Current (from previous listing photos):

Design top view and some ground level views:

Appreciate any advice or alternative ideas.