Answer

In the common 47-day Updhan vidhi, the practice is one day of upvas and the next day of ekasan/Nivi, repeating alternately. So, if the 47-day Updhan starts with an upvas day, the total is 24 upvas and 23 ekasan days. Because 47 is an odd number, if a sangh starts with ekasan instead, the count can flip to 23 upvas and 24 ekasan days. ( jainworld.jainworld.com)

Explanation

The guideline states that during Updhan, one must fast on one day and do ekasan on the second day. That alternating rule is what determines the count, so the exact number depends on which observance begins first. This is an inference from the standard alternating pattern. ( jainworld.jainworld.com)

Takeaway

So the usual answer is 24 upvas in 47 days, if the Updhan begins with upvas. ( jainworld.jainworld.com)