What does K mean when selecting a image size on my Nikon d3100?

E.g Image Size Small, 1.1mb, 6.7k

Image size is measured in bytes. K means Kilo meaning thousand so 6.7kB actually means 6, 700 kilo bytes. M is mega which stands for million.

Actually K = 1024 and M = 1048576 in computer speak as it is derived from memory cell structures which are binary.

But for most conversations, K (kilo) = one thousand, and M (mega) = one million.