Occassionally it is useful for the user to override the value of a uv variable. This is especially useful if the value of the variable is both wrong and important! When uvio opens an old file, for each variable name that is present in the uv file, it checks if there is a corresponding item with the same name. If there is, then the value of the item is used to override the value of the variable. Unfortunately the item must consist of a single number, and this single number will be copied into each value of the variable (if the variable consists of several elements).