On the Move, page-33

There are two types.

1. IMC (Issued Market Capitalisation) where the total issued stock x market price per stock.
(Does not include company options).
2. FFMC (Free Float Market Capitalisation) where the total issued stock minus restricted stock x market price. (Does not included company options).

You are both right, too some degree. The HC MC appears to be using version 1. derived from somewhere else I suspect Yahoo Finance.