A lot depends on whether you have the drop down box where you an make named lists of your own choosing.
If you only have your Watch List you only have 200 items.
If you can make up your own named lists you can have 50 lists, including your Watch List with a total of 200 items on each list so a total of 10,000 items. I currently have in excess of 1200 items on my combined lists...the most I have ever had was about 1300.