No - the "12 slots" bit is directed at brand new players, who'll be given 12 slots more than the zero slots they start with. 
If you already have a game account, no extra slots are added.
cheers thanks for the info
Brushing twice a day keeps the Strep.mutans at bay!
If you play on Defiant Server send a tell @Electro Kitty to join The Wonder League SG
I realise if i buy the MAC edition and apply it to my existing PC account that it will upgrade the account and give me the Valkyrie costume parts and the mission transporter but can anyone tell me whether it will also give me 12 extra slots per server?
Brushing twice a day keeps the Strep.mutans at bay!
If you play on Defiant Server send a tell @Electro Kitty to join The Wonder League SG