It's the admin for the Department, if there is no actual "admin" for the department, just choose the system admin (and uncheck the Department Admin box).
Hope this helps
Actually, after much experimenting, my previous response was wrong.
Under " Alerts & Notices"
New Ticket Alert: Enable Disable
Select recipients
Admin Email | Department Manager | Department Members (spammy)
"Admin Email" does not mean the department manager, nor does it mean any and all admin staff (which is what I originally assumed it meant) . It means "System Admin" The System Admin Email Address is entered a few lines up in the admin control panel. scp/admin.php?t=pref
It really should be corrected to say
System Admin Email | Department Manager | Department Members (spammy)
This can be changed in line 314 of /include/staff|preference.inc.php