Even if you say that they have 140 million users, that still does not mean that have 7% market share if there are 200 billion users, because many users have multiple browsers installed. To simplify things, assume you have 10 users:
- 10 of them have Firefox installed
- 5 of them have Opera installed as well
Since there are 10 users, is it fair then to say that Firefox has 100% market share? Does Opera have 50% of the market share? In other words, your number of 7% is a drastic over estimate.
In addition, I don't think "people are focusing solely on the desktop and North America". The stats I listed are Worldwide and Europe only, exactly the opposite of what you are stating.