I spotted a mistake in Window Calculation documentation as below
I did a test to better understand each scenario (unbounded following, current row, offset following) for Upper Bound. Hope this is helpful for some users having the same doubts.
o Lower Bound = unbounded preceding
Upper Bound = current row
Line 2 with current row is 82 (airtime): avg time = (76+82)/2 = 79.000
Line 3 with current row is 88 (airtime): avg time = (76+82+88)/3 = 82.000
o Lower Bound = unbounded preceding
Upper Bound = unbounded following
Avg time = avg(airtime of all same region in the window)
o Lower Bound = unbounded preceding
Upper Bound = offset following (offset value =2 rows)
Line 1 avg time = (34+34+34)/3 = 34.000
Line 2 avg time = (34+34+34+35)/4 = 34.250
Attached is sample job (detail in Window calculation and Rename components)