Reference:
ATS8553
Midsize Pack: License for 20 Client Operators and a maximum of 10,000 ATS Advanced or ATS Master Centrals, 2 Communication Servers and Automatic Task Scheduler. Characteristics of the necessary computer equipment (not included): Net Framework 3.5, Windows 7 & 8 (32 & 64 bit), Windows Server 2008, SQL database MS SQL 2008, 2012 (limitation to 10 Gb in events), for installations from ATS8552 we recommend the standard edition of SQL Server.