I've been doing some reading on the thread below (seems like this may have been the site & thread where the challenge originated) and opinions are split. Some folks are saying that 1 shot at each of the "X" marks should count as a perfect score.
But then I read this: "I think it is easier to shoot one shot into the white on individual targets than shooting 5 rounds into one target. My reasoning is that it is more difficult to sight in on a ragged hole than to sight in on a well defined black dot. I know it doesn't sound like a big deal but at least to me it seems to be easier."