In the future, a planetary crisis such as a severe global climate what percentage of the population are heterozygous

I found the full exercise on the internet. Bellow is the full text of the exercise.

"In the future, a planetary crisis such as severe global climate change may force human kind to travel across the galaxy looking for a new home. Suppose in the year 2317, a group of 507 human pioneers colonize a very distant and arid planet, Diaptomus Prime. This population has native life forms. In a population of native Diaptomus Primians, long antennae exhibit complete dominance over the short variety. The alleles that regulate antennae length are L (long) and l (short). In a population of Diaptomus Primians with a total of 100 individuals, 9 have short and 91 have long antennae. Assume this population functions like life on Earth and is in Hardy-Weinberg equilibrium at the antennae locus. Individuals with antennae of different lengths seem to have the same fitness. In this population the frequency of the long antennae phenotype is:"

The frequency of the long antennae phenotype, in this case, is calculated by dividing the number of individuals with long antennae by the total number of individuals.
individuals with long antennae ÷ total number of indivduals = frequency of the long antennae phenotype <=> 91÷100=0.91
The frequency of the long antennae phenotype is of approximately 9 out of 10 individuals.