ASA5512 can hold up to 250 simultaneous VPNs of any type: IPsec Site-to-Site or IPsec Remote access, or Anyconnect VPNs using SSL or IPsec IKEv2, or even Clientless VPNs.
That means, that you can use 2 Anyconnect premium + 248 IPSEC Site-to-Site VPNs. Or, for example, 200 simultaneous IPsec Site-to-Site VPNs + 25 VPN Client (IPsec IKEv1) + 25 AnyConnect VPNs (SSL or IPsec IKE v2). But no more then 250 at the same time.
"AnyConnect for Mobile" is currently out-of-date license. The license schema for Anyconnect was changed dramatically at the beginning of 2015. You can check the new schema here:
With new schema, if you need to connect mobile devices (iOS, Android and so on), using Anyconnect client, you just need to have Anyconnect PLUS license for neccessary amount of users/devices. Anyconnect Plus license will open following lines in the output of show version:
AnyConnect Premium Peers : 250 perpetual
AnyConnect for Mobile : Enabled perpetual
AnyConnect for Cisco VPN Phone : Enabled perpetual
Advanced Endpoint Assessment : Enabled perpetual
But, in spite of the output "AnyConnect Premium Peers : 250 perpetual", you will have the right to use not more then ordered amount...
If you need some advanced features, for example, Suite B Cryptography or Clientless VPNs, you need to order Anyconnect Apex license for neccessary amount of users/devices.
For ASA5512 you need to order Anyconnect Plus or Apex licenses, but no more then for 250 users, because ASA5512 won't support more then 250 simultaneous connections.
If you want to use Anyconnect client for mobile devices, and you are going to use IPsec IKEv2 for VPNs, you also will need to order Anyconnect Plus or Apex licenses.
Hope this helps.