Praudhamanorama p190

p190

[On the word] 'asmāt': Here, 'avyaya' was also read by the older grammarian; but that has been disregarded, because indeclinables are generally devoid of gender, and an avyayībhāva compound, even though neuter, lacks any other gender.
[On the phrase] 'vastutastu' ("In reality, however"): Because there is no plural to indicate predominance of meaning, the substitute traya is proper even when [the word is] subordinate in meaning, just like the [substitute] anaṅ for asthi, etc. This is the idea.
[On the statement] "akāro vaktavyaḥ" ("The substitute a should be stated"): And so, in the absence of plurality, the word auḍulomi ends in the vowel i. But in plurality, it ends in the vowel a. One should not be deluded into thinking that the word uḍulomi ending in i becomes ending in a in plurality. ... Thus ends the section on stems ending in i. ...