You are correct in your understanding of the Shrenik Tap (also known as Shrenikji Naam Tap), which is a significant and difficult austerity observed in the Jain tradition. This vrata (vow) is inspired by King Shrenik (Bimbisara), a great devotee of Lord Mahavira, who performed this austerity.

The Shrenik Tap is traditionally observed over 110 days.

• During these 110 days:

- 27 days are Paarnas (days when food is taken after a fast) - 83 days are Upvaas (complete fasting days, where no food is consumed from sunrise to sunrise)

The pattern typically involves alternating fasts of varying lengths (Attham, Atthai, and Chauvihar Upvaas) with Paarnas in between, but the total remains 110 days: 83 fasting days and 27 Paarnas.

This Tap is considered extremely difficult and is undertaken by very few, usually under the guidance of a Jain monk and with proper understanding of Jain fasting principles. It is believed to result in immense spiritual merit (punya) and purification.

References:

• Jain Granths/Texts describing Shrenik Tap
• Popular Jain calendars and almanacs
• Oral tradition, discourses by Acharyas and Jain scholars

Note: Such austerities should be undertaken only after consulting with knowledgeable Jain monks or scholars, ensuring one’s health and spiritual preparedness.