PSUs question

I am buying a new power supply and i'm not sure how to

notice the amperage on the 12v rail for my videocard,this are some specs of the 12Vina PSU:

Topower - 550W p5

12V1 12V2 (Voltage)

20A 20A (Max split current )

35A (Max combine current)

420W (Max combine power)

So this PSU has 20A or 35A for a videocard?

And also when a card recommends a 450W PSU,it means the max combine power of the 12V or the general wattage(550 in this case)?Thanks.

look on the side of the box it will say something like

12v+1 = 18a

12v+2=18a

just added them up and maybe minus a couple.