A lot happens, but is it hard to accuse the AI of linear thinking. The creative process is a tangled form.
The algorithm starts thinking in raw pixels:
Even at only 8x8 pixels with 8-bits per color RGB, there are (2^(8*8))^3 possible designs. We render at 1024x1024, which means there are over 10^946958 possible designs. By contrast, there are only about 10^82 particles in the universe.
The brain has over 100 billion brain cells with all sorts of connections. While the AI doesn't have as many cells, it can process information faster. Computations are done with GPUs for maximum throughput.
8 NVIDIA Tesla V100's are used. These can process 900GB/s at up to 125 terraFLOPS. The GPU is really fast at arithmetic.
Watch the GPUs at work:
And creation slowly takes form:
Eventually, designs are put onto apparel for full formation: