Looks like an error on Sarna.
Historical: Operation Klondike p. 105 says "Andery did well at the Eden Military Academy" and "Andery was assigned a staff role, but he chafed under the restrictions and instead became an observer with the Wolf forces on Eden. It was there, as the campaign drew to a close, that Nicholas' brother died, ambushed by a larger enemy force."
So both the fiction and the Historical place Andery's location pre-Second Exodus and during Klondike on Eden.