28 AWG is fairly typical I think, 7 strands. Certainly I would estimate the one on my bench to be that and I think I counted 7 strands. I don't think I can measure that accurately though to get the area of a single strand to calculate it properly though.
Correction I didn't notice the one linked was XH. I measured some plain IDC ribbon wire which was 28AWG/7, and also some ribbon with dupont and that was about the same, maybe thinner, hard to tell. But as Nusa says, the one in your picture is actually marked as 24AWG (of course, is that trustworthy, is it actually what you'll get, who will know) which makes some sense as they are XH connectors and should be able to carry more current than ribbon is usually used for.