48. ithilE chathurththiyERik kazhiyum.
It is taken that the fourth case is hidden inside the akAram.
Sri PBA Swami's Sarartha Deepikai:
Thus far the meaning of the akAram has been explained. Now, Sri Pillai Lokacharya takes it that a vibhakti (case) is present in the akAram and begins to explain its meaning. The fourth case (chaturtthi vibhakti) is hidden inside the akAram.