No, you cannot re-enter the Schengen Area since you have used up the 12 days allowed.
The visa allowed you to enter the Schengen Area multiple times, within a 1 month period, to stay a maximum of 12 days.
This would have allowed you to arrive in France and stay in Paris for 2 days, after which going on to the UK (leaving the Schengen Area) for a few days and then take a train to Brussels (re-entering the Schengen Area) to stay a further 10 days (or until the month is over).
Partial days, for entry/exit, count as full days.
This is different from visas issued by some countries, where the visa allows you to apply for (some form of) leave to enter at their border while the visa is valid. The immigration officer will then decide if and for how long you may enter.
For a Schengen Visa, this leave to enter and the time allowed has already been granted. If no duration period is given, you are allowed 90 days in any 180 period while the visa is valid. You may still be refused entry for other reasons, but rarely will the amount of time be reduced.