What unit of measure is MM?

Question

I am reading this report and there are plots like this:

What unit of measure if MM? Because I don't think is millimiters and in general you indicate "Millions" with a single M

Answer 1

Some people use MM to designate Millions. It makes it clearer that M doesn't mean thousand. Of course mm also is millimeter, and MM is 2 thousand if we were using the roman convention.

I have seen this is financial articles, so it is sort of money related.