Their goal is not the distribution of net beds. Their goal is the distribution of net beds which are then used. So obvious that you didn’t mention it, but without mentioning it any contribution yields a net bed and nobody in it. Thus worse than no contribution at all. Since you must consider time frames longer than ‘distribution of net bed’ you now have to ask when you draw the line. Distribution then use then stop? Distribution then use then research into outcome of use then stop? Where you draw the line is your choice. If you draw the line at the right place you can have any outcome you like in an infinite universe. Distribution of net bed then use then 100,000 generations later a distant relative of a sleeper in a net bed did a great deed. Or an ill deed.
Which is a longer way to say it matters as much as and in the way you want it to who you donate to in an infinite universe.
Further, you are in ‘the world’ that will change if you make a donation. If you are very moved by a donation then the donation size might matter less. If you donate much but don’t care then ‘the world’ is changed in that way.