Critical Path When there is a folder with expected time and buffer

Hi,

I have a case where in one diagram, I have a folder which has a subdiagram in it.
In plan mode, After running the analyze as a project tool, I can see that under the time label it says: 8d (36d).
I assume this means: expected 8 days, but with the buffers, it actually becomes 36d.
Now, in this case, the path containing this folder is supposed to be the critical path because all the other paths are less than 36d.

However, the program keep insisting that the path with the most expected time is the critical path. For example, I have a path in the same diagram that has an expected time of 9d. It will always pick this path as the critical path, even thogh the duration and end date of the path with the above folder is clearly later than this path.

Because it always chooses the path with the highest expected time as the critical path, when running the analyze as a project tool it always ask for a time buffer on the path with the folder, but the time buffer becomes messed up with negative numbers.

It seems that critical path calculation only takes into account the expected time, but not the effects of the buffers. Is this intentional? If so, could you explain why ?

Thanks.