Graphics Cards

[Emkay]

My question is quite simple. how can a gpu take more than 400 watts via 2 x 8 Pin and 75 watts from PCIE ?

it has 3x 8pin connectors. Those are Connected via 2x 8 pin coming from the PSU which theoretically provide 300 watts.
plus the 75watts from pcie makes 375.
now, how can i draw more than 400 watts ? is there anything im missing or how can this card draw more than i supply to it?
i know that the card doesnt know how its connected, so its just drawing power, but is this dangerous?
because 375 watts total power is the safe specification over 2x8 pin and 75 watts over pci.
in total it can draw roughly 425 watts. did i miss or get something wrong here?
is my knowlegde about pcie 150watts per connector wrong?

i made a simple image to show how my card is connected.
is this dangerous in any way? because the card can draw more than totally ,,safe" provided to it.

[goodplay]

This from Corsair,

[goodplay]

That usually applies to the top tiers psu, older lower quality (no name brands) are more than likely less capable.

Personally, i would be using 3 separate cables. 

[Emkay]

i have a corsair tx 850m.
it only has 2x pcie 8 power plugs.
i have two seperate cables coming from it. and both are connected. one chain is not. just like the image above shows. so if 1 cable can provide up to 288watts and i have 2 connected (the second one is chained), i should be good. i had a rtx 3090 connected to this power supply which spiked to 450 watts. but i am not sure about this 7900 xtx.

anyway, i dont want to get above 400 watts, because that is just nuts just for gaming. i currently sit on a undervolt and standart clocks. no issues for now, and honestly, i dont think it will make any problems. but we'll see.