The usual ammunition bag for the MG34 was called the "Gurtsack" and in the Rye Field interior it is part M8.
Rye Field's instructions tell you to put two of these bags on the turret wall.
Their turret wall has notches for exactly two bags.
They apparently took their cue from this WW2 photograph. It shows two bags in exactly those positions.
But if we take a close look at the inside of a Tiger, we find that there are actually 4 positions. That strip of metal is dedicated to ammunition bags.