My first edition RB says:
II.2 The German Perimeter for the start of the Initial Scenario is defined as Hex Grains W1-W5-U6-U25-Q27-Q29-M31-S40-S45 (with the two map-edge hexes being W1 and S45). The Russian Perimeter Area consists of all Locations east of the German Perimeter. No No-Man's-Land hexes exist. Each side should place friendly map-edge Control markers as appropriate (11.6053).
Given it states it as the German Perimeter, use the alternate hex grain that gives the German the most area. It gives them one hex in the factory building.