Rdp Clients Server 2012 r2

Hallo,  

I habe the following question. With Server 2012 r2  You can use 2 Rdp Clients at the same time. if i need more 

I have to buy rdp cals. if i buy one count this as three rdp Clients ? or is this still one User ?

I need 5 rdp user at the same time 

Thanks for your help 

Meyerhans