A root-aṅga (stem) ending in ā gets the augment yuk (y) before the Aorist sign ciṇ which causes also the vṛddhi of the root-vowel.,
As अदायि, अधायि with चिण्, दायः and दायकः, धायः, धायकः with ण and ण्वुल् ॥ Why चिण् and krit only? Observe ददौ, दधौ in the Perfect, and चौडिः, बालाकिः with इञ् a Taddhita affix 4.1.96. So also ज्ञा देवता अस्य = ज्ञः ॥,