You can delete any of the plans you do not need for the project. Simply put a check mark in the upper left of each thumbnail image, and click the trashcan icon
TIP: You can select multiple thumbnails at one time. Press Shift on your keyboard and put a checkmark in the corner of the first plan. Then click in the center of the last plan (click View, instead of putting a checkmark in the corner). This will select all the plans in-between.