Well in my opinion it is doing so that gives a wrong Bar as building 1:00 the 1H Bar in that way we consider the 1:00 1M Bar has ended which is not the case as it will end at 1:00:59...I do not understand the logic behind as Zorro builds the 1:00 1H Bar when setting BarPeriod=60 using 1M Bars from 00:00 to 00:59 which in that case is correct in my mind.