I think they are telling you to deploy as far you can, so you have to deploy at 40m of distance from the portal. The resos will be at max distance positioned, so will be more "difficult" to destroy.
But as is said, "A picture is worth a thousand words:"
EDIT:
Is good to prevent attacks from UltraStrikes deploying 1 resonator at less than 40m, I ussually deploy more or less 1 resonator at 10/15m. With this type of deploy if someone attacks with ultras to the center of the portal, the range of attack of Ultra will hit the resonator, so it will make the portal attack the player.