Jamieson, Fausset and Brown on Numbers 26:54

54. To many thou shalt give the more inheritance--that is, to the more numerous tribes a larger allotment shall be granted.

according to those that were numbered--the number of persons twenty years old at the time of the census being made, without taking into account either the increase of those who might have attained that age, when the land should be actually distributed, or the diminution from that amount, occasioned during the war of invasion.