The term 'fire generator' was coined to explain the function of Ga2-26, viz. to initiate the 31 period long calendar beginning with Ga2-27:
Ga2-22 Ga2-23 Ga2-24 Ga2-25 Ga2-26
period 1
Ga2-27 Ga2-28 Ga2-29 Ga3-1
Ga3-2 Ga3-3 Ga3-4 Ga3-5