[Not a bug]damage suffered while preventing damage

[BAgate]

Describe the Bug:
Don't know if this is just bad interface (or me not understanding it), and I have a vague recollection of reporting this before but couldn't find t, so here goes.

I have Atalya, Samite Master in play as well as a creature and a City of Brass. The 2nd creature suffers damage and after declining instants we get to damage prevention phase. I click Atalya, Samite Master and it asks for mana, I click on the City of Brass and suffer 1 damage and am asked if I want to use damage prevention. When I decline all damage goes through, so I am left with a creature that has already suffered damage and an Atalya, Samite Master that is being activated with no damage card to target.

Which card did behave improperly ?
non-specific

Which update are you using?(date,name)Which type(Duel,Gauntlet,Sealed Deck)
Manalink 2014/12/20: Commanding 2014 Urzas,duel

What exactly should be the correct behavior/interaction ?
Declining to use damage prevention should not cause all damage to go through, it should just move on to whatever was coming next.

Are any other cards possibly affected by this bug ?
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[Aswan jaguar]

The other topic you remember that has to do with the same problem with another card that prevents damage is this about Shining Shoal - City of Brass:
viewtopic.php?f=86&t=11429&p=148881&hilit=City+of+Brass#p128635

It is kind of bad interface and designs choice I believe.You get confused from the new damage prevention card that is generated by City of Brass damage that kind of makes you think that this new damage prevention phase is only for the new damage made by City of Brass.In fact if you pay attention you will see that damage card from damage made by City of Brass is added and you have both damage cards in the screen and also the mana from City of Brass has not been added to the ability but emptied to your mana pool you can tap other lands or mana producers so when new damage prevention phase asks for them you have to reselect them and then you can select the damage card from the creature just fine.The original menu asking you to tap mana to prevent damage will appear again baffling you as you have already done this.This has to be a trick made by Gargaroz do deal with the original bug I submitted for Shining Shoal it is confusing but works.

The bug is that in contrast with Shining Shoal, Atalya, Samite Master mustn't trigger damage prevention effects for damage made to players in the first place as it prevents damage made only to creatures.