Okay so it sounds to me like you have each EA studio in a seperate tab on the same browser rather than on seperate browsers? If so then that is the problem. The several hundred will just have been generated in the brief moment that the tab was active. Can you confirm if this is the case or not?
As for the portfolio, stick to 100 at most I would say personally. Do you have any great need for anymore than this? If so can you give a little more detail on your system?
100 per portfolio will be absolutely fine (optimal is possibly dependent on how many positions open at the same time but I would need to test this, however don’t feel its really necessary).