Vanija is sixth in the rotation and takes positions 7, 14, 21, 28, 35, 42, 49 and 56 of the sixty karanas in a lunation.
By the standard rule, position p sits in tithi ceiling of p over two, in the first half if p is odd and the second if p is even. Vanija therefore holds the first half of tithi 4, the second of 7, the first of 11, the second of 14, the first of 18, the second of 21, the first of 25 and the second of 28. Four fall in the bright fortnight, four in the dark.
Position 56 puts it second to last in the rotation, immediately before Vishti at 57 and therefore two half-tithis before the fixed block that brackets the new moon. In electional practice that adjacency matters: an activity being timed away from Vishti at the end of the waning month has Vanija as the nearest preceding option, and the whole run from position 56 through to position 1 of the next lunation is a stretch of five consecutive karanas in which only one, Vanija itself, is generally read as favourable.
The clock figure is the same as for every karana. One sixtieth of a mean synodic month is 11 hours and 49 minutes, with an actual range of roughly ten to thirteen and a half hours according to the Moon's speed at the time, which is why an almanac publishes the ending moment of each karana rather than a duration.