Two plants with an inated seed shape produced 340ospring. Of those 340, six ospring had a constricted pod shape. What are the genotypes of the parents?

The dominant phenotype is inflated seeds, expresses by genotype II and Ii. The dominant allele hides the expression of the recessive allele, so if the genotype has at least one dominant allele, the phenotype will be inflated.
The recessive phenotype is constricted seeds, expressed by the genotype ii. In this genotype there is no dominant allele, so the recessive allele can be expressed.

The individual with constricted seeds must have two recessive alleles i in its genotype ⇒ ii.

One of the i alleles was inherited from one of the parental plants, while the other parental plant provided the other i allele. So both parental plants must carry the recessive allele in their genotype.

We know that both parental plants have inflated seeds, which is the dominant phenotype.

So, if both parental plants have inflated seeds and also carry the recessive allele, then the parentals´ genotype must be heterozygous, Ii.

Both plants exhibit the dominant inflated phenotype but carry a recessive allele which will be provided to some of the descendants. These last individuals will have constricted seeds.