Why do some karyotype graphs contain 46 pairs of chromosomes?

They both contain 23 pairs of homologous chromosomes (and... yes as Luis suggested the first one is male and the second one female).

In Figure 1 each chromosome is composed by 1 chromatid, while in Figure 2 each chromosome is composed by 2 chromatids. This is probably because the two pictures were taken at different stages of Mitosis.

In Figure 1 the picture was taken probably in anaphase, while in Figure 2 was probably taken in or before metaphase.

You might want to search the internet to check the difference between chromatids and chromosomes and to read something about the cell cycle and mitosis.