Manufacturing Lead time issue

Summary:

Manufacturing Lead time not correct when resource is available in one of the shifts out of multiple shifts.

Content (please ensure you mask any confidential information):

Manufacturing Lead time for a work definition is not coming correctly.
The resource usage in the OP is 16 hrs and this resource availability is
for 1 shift out of 2 shifts each 8hrs. When we ran the Calculate
Manufacturing lead time it calculated the time as 1.5 days. As per the
Oracle functionality variable lead time = (resource total usage/ total
shift duration)/ Lot size.
Lot size = 1

Please check and let us know why Oracle is calculating the lead time in such manner and not following the standard logic.