Help me understand GPU vs slot size

I am ordering parts for a streacom da2 I can see in this post forumthreadspage-40#

Slot Gpu2 Slot Width Standard Gpu ComparisonBest 2 Slot GpuGPU Engine Specs:CUDA Cores1920Boost Clock 1680Memory Specs:Memory Clock

25h slot We normally recommend GPUs with slot requirements We have seen others manage to squeeze cards, but it will be a tight squeeze if

25 coins slot slots with three phases, and Internal ” Bays 2 Expansion Slots 3 Max PSU Length SFXSFX-L Max CPU Cooler Height 140 mm Max GPU