Microsoft FastTrack eligibility

I'm looking at Office 365 Business Premium for a company with 30 users. 

This TechNet article (https://technet.microsoft.com/en-us/library/mt651701.aspx) states that we could use Microsoft FastTrack with this plan but what exactly does it mean when it says "if you purchase at least 50 licenses for an Office 365 tenant". 

Would we only purchasing 1 license for this company with 30 users, or does each user get a license so we could have 30 in this case? Can a tenant have multiple companies? 

Hope this makes sense.

Thanks