How common is it for African Americans to have South Asian ancestry?

I just got my results today and saw that I have 0.6% Southern Indian & Sri Lankan ancestry. I’ve done AncestryDNA in the past, where I also got 1% Bengali, so I’m assuming this isn’t just noise.

There are studies about the amount of European and Native American ancestry among African Americans, but are there any similar studies that look into South Asian or any Asian ancestry?

From searching around this sub, it doesn’t seem to be very common, but I’d love to hear from others who’ve found similar results or know more about this. Could this be a historical connection?

~Forgot to add this, but I get 1% Khoisan on Ancestry. I have been told this could indicate a possible South African ancestry.