Relation between task duration and project calendar work hours

DRogith - I'd probably need to see the calendar, know the time zones and the exact steps you took to enter data into the plan, and also know the resource calendars and time zones  (You mention them but do not show any assignments).  Using the steps you describe above I get this plan:

Project for the web hard codes the duration into hours, based on 8h being a day currently, so assuming the project start date was set for 10/11 and the duration was entered as 6 days it would generate a finish date of 10/26 - as it takes 12 days to complete the '6 * 8h' based on the 4h per day calendar.  All the others then follow as expected, with the same logic, and my final task also starts at 5pm.  Feel free to open a support call to have one of our engineers dig deeper with you - after all support is included with the subscription.  I also did a couple of recent posts on the calculations on the Project Support blog at https://techcommunity.microsoft.com/t5/project-support-blog/bg-p/ProjectSupport .  For the final task to start at 10am suggests a different calendar is in place on 11/6.  I don't see any assignments but if there are then those assignees calendars would take precedence over the project calendar.  In my case if I assign myself to task five it will then start at 9am.  Maybe your resource for Task Five has a different time zone than you think?

I've actually got the Project Accelerator loaded so mine looks a little different, but this makes no difference to the scheduling - I chose the default fixed duration schedule mode when creating the project.

Best regards,

Brian.