How does meiosis 1 make haploid cells when the DNA was replicated before division?

Answer 1

After meiosis 1 - the chromosome number is halved (= haploid) but the chromosomes are composed of two chromatids = 2 DNA molecules.
Haploid refers to chromosome number and not DNA content.

Answer 2

1 diploid cell (2n) cell becomes 4 haploid (n) germ cells (eggs or sperm). During meiosis, chromosomes are replicated once in S phase (just like mitosis) into sister chromatids, but the cell divides twice.