VNTR profiles may present either a single band or two bands. If two bands are present then the individual is a heterozygote for these two bands. However, if only one band is present there is ambiguity as to the true genotype of the individual. This person may be a homozygote in that he has two copies of the same allele, or he may be a heterozygote for two very close bands that cannot be separated on the gel. The second NRC report proposed the use of the '2p' rule, or Formula 4.10a in the sub-structure case, as a conservative upper bound in the statistical interpretation. However, further examination suggests that these formulae are not necessarily conservative. In this paper we examine this phenomenon by deriving a formula that contains both the corrections for null alleles and for subpopulation effects.