Before karyogamy, each haploid cell has one complete copy of the organism's genome, while after fusing together, the resulting single cell is diploid, containing two copies of the genome.
Each haploid cell has one complete copy of the organism's genome. This was before karyogamy. The resulting single cell is diploid. This was together. This was after fusing. This was before karyogamy. Each haploid cell was containing two copies of the genome. This was before karyogamy.