Praudhamanorama p13

p13

'hrasvadīrghaplutaḥ' is an aggregate dvandva compound (samāhāradvandva). The masculine gender is Vedic [irregularity] belonging to the sūtra. 'Like the duration of v' (vāṃ kāla iva): this is a statement of the resultant meaning. But the analytical paraphrase should be understood as: 'he whose duration is that of v' (vaḥ kālo yasya). By the word 'ū', the duration of its own pronunciation is metaphorically indicated.
uccairudāttaḥ (Pāṇini 1.2.29)