MS Project Summary Task duration doesn't show correct value...

So I have a group of tasks/subtasks that I've been working with and I cannot figure out why the duration doesn't add up.

Let me start by saying that I'm open to the possibility that I've misunderstood how to set something up or that Projects wasn't designed to do this or even that this IS a "correct" answer and I'm just not thinking about it correctly.  But beyond the gripe that there should be an option to force individual tasks to start on a new business day (because frankly, that's how things work in the real world sometimes), I cannot figure out how Projects is giving me the number it's giving me and I'm about a half a day into trying different settings and combinations of settings to get this to resolve.  I've confirmed the behavior by creating a generic version of one of the summary tasks in a new file and got the same results.

     I have a group of tests I'm trying to schedule that all have component parts, i.e. Summary Tasks and Performance Tasks.  A group of these tests involve long durations of continuous testing.  By continuous I mean 24 hours a day, 7 days a week.  There are preceding and following tasks that are part of each test for setup, tear down, report writing, etc. that are all "regular" schedule items.  By regular I mean 8 hours a day, 5 days a week. 

1. I have a summary task we'll call Parent.
2. Under it are three consecutive (A is a predecessor of B, B is a predecessor of C) tasks, Task A, Task B, and Task C.  A and C are regular schedule tasks, but B is a 24/7 task.
3. Everything is set to auto scheduling and I have a resource defined, Lot A, that has its calendar set to "24 Hour" that's been assigned to Task B.
4. I go through and set the durations to 1 Day, 6000 Hrs, and 1 Day for A, B, and C respectively.  6000 Hrs is 250 Days.
5. With a start day and time of today, 12/16/2019 8:00 AM, it shows task A going from 8AM to 5PM on the 16th (correct).
6. It then shows Task B starting immediately afterwards (which is understand able since it is on a 24 hours schedule, and this is probably how it would start in real life) and runs continuously from 12/16/2019 5:00 PM until 8/22/2020 5:00PM (correct).
7. Just as a sanity check I did use Excel to add 250 days to 12/16/2019 and 8/22 is the right end date.
8. Task C then starts on 8/23/2020 at 8:00 AM because Task B ended at the end of the regular working day (correct).
9. All in told, I count 251 days total, start to finish.  BUT the summary task (which shows the correct start and end times) says the duration is 181 days???
10. I tried setting all of the calendars explicitly for each task including the summary task.  Still get 181 days.
11. What's weirder is if I set the calendar for the summary task to 24 hrs, the duration jumps to 757.13 days???  I think I kind of understand where that might be coming from.  If you consider each 8 hours of the 6000 to be a day that would turn the 250 into 750 days, but how the other 2 days become 7.13 days I'm not at all clear.  Either way though, this doesn't make any sense.

     So what am I doing wrong?  Is it me or Projects that has this has this wrong?  How can it show all the correct start and end times and then turn around and have the duration of the summary task wrong?