Use this button to enter manually a new size to the list of fixed sizes. Note that there exists also an interactive method for specifying non-standard fixed sizes.
Use this button to delete the currently highlighted fixed size from the list.
Use this button to move the currently highlighted fixed size up. Note that last used fixed sizes are automatically put at the top of the list.
Use this button to move the currently highlighted fixed size down.
Use this button to reset the set of fixed sizes to the standard list.