Slitherine

When one has a group of LF archers (8) for legion support, third rank. Are these archers part of that Particular BG? I was playing a game and and my friend thought that they were one group of eight tied to the battle line and that the BG'S could not break off in different directions and have the archers stay with the BG. (?)

They are part of the BG - e.g. a BG could have 4 bases of legionarii and 2 bases of supporting archers.