it's the maximum amount you can cashout from the promotion, (ex: even if you manage to make 10mBTC you'll be not allowed to withdraw more than 2mBTC.)
It is the minimum withdraw amount, go to your account and then try to withdraw. You'll see a message like in this below image:
The 2mbtc is indeed a max amount to withdraw from the promotion but it is also a minimum amount to withdraw. If you say that the minimum withdraw is not 2mbtc, have you successfully made a withdraw under 2mbtc?
Unfortunately, when I used promotional codes and then tried to achieve the minimum rollover, in the end I lost everything I had managed to win.
The minimum withdrawal is really high. I wonder if you can make a deposit to top up the amount to 2mbtc and then withdraw it..?