Narapatijayacarya 3.1.56

Having converted everything into palas, when divided—apportioned—by its own duration, [which is] a twelfth part, whatever quotient is obtained, that number is to be known as the elapsed states; the remainder is the present state. As for the remainder, by calculating the past and the to-be-traversed: when the past is multiplied by sixty, it is the elapsed time; when the to-be-traversed is multiplied by sixty, it is the remaining time. Another example: as on the first day of the waxing fortnight of Caitra, the elapsed ghaṭikās are 33. On a tithi, the measure of the twelve states is five ghaṭīs. When divided by five as the divisor, six traversed states are obtained: 6; the remaining ghaṭīs are 3. The seventh state is [currently] present. In Sadānanda’s daily routine, the phoneme-sound is the vowel 'e'; under its influence, the first tithi is an infant state for Sadānanda. By that power, it becomes the kingdom-giving state. Through this example, the result of the states for all [persons] is to be determined. "Mute and child, etc.": the names of the states are written, and it is easy [to understand].

Now he speaks of the directional sound in battles and the like:

The vowel 'a' is the lord in the east; likewise, the vowel 'i' is in the south;
the vowel 'u' is to be known in the west; 'e' is in the north; the sound 'o' is in the center.

In whichever direction the sound rises, its fifth direction
one should avoid in all undertakings, especially at the time of a military march.

If the stationary querent asks towards the direction in which the sound has set,
loss, death, fear, and defeat occur; of this there is no doubt.

"East", etc. is clear. "In which", etc.: On whichever lunar day whatever sound rises in whichever direction, beginning with the east, one should avoid the fifth direction from it in all undertakings. Especially at the time of a military march, one should not go there. Regarding "one should avoid the fifth direction", among the eight sounds beginning with the mātrā, by virtue of which of them one should avoid the fifth called "dead"—nothing is stated. Here the intention of the poet is understood in this way: precisely from the phoneme-sound. That is, whichever phoneme-sound belongs to someone, that is his direction; one should avoid the fifth from it. Thus has the commentator on the Jayalakṣmī explained. The example there: As for Devadatta, the fifth direction is the north, therefore Devadatta should always avoid the north in travel, battle, and dispute. In battle, in the midst of an army, he should not take resort in that direction. But Narahari [explains] thus: as the sound i rises in the southern direction on the second, seventh, and twelfth [lunar days], the fifth direction from it is the east, so one must not go there, because the sound a, which is the dead sound, rises there. In the doubt as to how the central direction is to be applied: on the first, sixth, and eleventh [lunar days], the rising of a is in the eastern direction; the fifth place from that is the center.