This is due to the Maximum Workflow List Items setting for the workflow window.  By default this value is set to 100 items, which is the combined total for the number of items listed in both My Worksteps and Worksteps Waiting in Queue.  The Worksteps Waiting in Queue directory in the left-hand navigation pane always displays the total workstep count.

To change the maximum number of workstep items that are displayed in the workflow window:

1. From the workflow window, right-click anywhere in the viewer and select Options.
2. Select System Settings.
3. Click the Workflow tab.
4. Increase the value for Maximum Items in Lists to a number that accommodates the needs for this user.
5. Click Save.
6. From the workflow window, click the Refresh button to update the lists to the new maximum item count.