Admin Center Administration

Hi team, this questions may have come already but I haven't find an answer yet. A big customer is looking to purchase a big batch of licences for chalk, they are concerned about how they can control the new licenses that some individuals in the company could purchase in the future. When buying different licences in different time spams, will there still be a single administrator for a defined company? or there will be one administrator for each license bought? 

Also will the Administrator account for chalk count as a named user or as a host? Or is there a way that the administrator only have access to control the admin center but is not able to consume the slots for the users or hosts?

Hope you could give me some guidance

VF