Step 1: Understanding the Concept:
Per capita availability measures daily milk supply relative to total national human population.
Step 2: Detailed Explanation:
According to the Basic Animal Husbandry Statistics (DAHD, Government of India), the per capita availability of milk in India during 2018-19 reached $394\,\text{grams/day}$, comfortably exceeding the ICMR recommended dietary allowance of $300\,\text{g/day}$ and the world average ($pprox 310\,\text{g/day}$).
Step 3: Final Answer:
Hence, the per capita availability of milk per day was 394 g.