If at any time during the turn a Space Marine can draw a line of sight to a blip (see Shoot Actions) then it is automatically and immediately revealed....allowing the Space Marine to see a blip. This would be involuntary conversion ...Placing Revealed Genestealers When a blip is revealed, one Genestealer is placed on the space the blip was occupying. Any additional Genestealers must be placed in an empty square adjacent to the first....while the Space Marine player gets to place the models if the blip was involuntarily revealed.
...So the answer would be: one genestealer is placed in the space of the blip, then genestealers are placed in adjacent squares to the first by the marine player, it there are less spaces available or not any genestealer models left in the box, they are forfeited. There is no mention of "closer to the marine".