First column listing elements in the Routing Unit
If = 1, there can be only one element in the Routing Unit, whose ID ( in ) is specified in this column. If > 1, this column is followed by additional columns listing the elements included in the Routing Unit, but those columns will not have a header. If there are several elements with consecutive numbers in a Routing Unit, they can be listed by specifying the first one in one column and the last one with a hyphen in front of it in the next column.