There are ##39## chromosomes in their haploid cells.
During I the ##78## chromosomes in a diploid cell line up at the equator of the cell. Note that the chromosomes have already replicated.
##39## chromosomes will then move to each pole of the cell. The difference between anaphase in meiosis I and is that in meiosis I the centromere does not split so the sister chromatids are still held together.
The result is ##39## chromosomes at the poles of the cell. The chromosome number is reduced from ##2n## (diploid) to ##n## (haploid). Then the cell will undergo meiosis II where the cell will divide producing ##4## haploid daughter cells with half the number of chromosomes of the parent cell.