If you make many mistakes and wish to start over, you will need to purchase additional sheets in the lab. Lay out the entire exercise in pencil on a paper worksheet before doing any ink work. Use the pen size or instrument specified. After the ink dries, you can gently erase any visible pencil lines with a soft eraser. After cleaning, hand in your work.
Errors are inevitable.
Part of the exercise below gives you practice with correction methods. You may also need to correct unintentional errors. If the specified pens are not readily available, a size one step larger or smaller may be used.