Network analysis find shortest route question

[TunvaPakkawat]

Hello, I'm studying Network Analysis.
I set the priority of a road from 1 (low) to 5 (high) the picture below

I'm routing from point A to point B using 2 methods. 
1. Route1 point A to point B: impedance = Travel time (find fastest route)
    result: 377.89 kilometers // 265 minutes // routing through road level 4

2. Route2 point A to point B: impedance = Kilometers (find shortest route)
    result: 512.16 kilometers // 345.97 minutes // routing through road level 5

My question are "why the route 2 takes distance and time more than route 1?" and "Is the result from route 2 should be the same route or close to route 1?"

[DavidPike]

I won't pretend to know much about the heuristic algorithm but I do think the hierarchy is causing the strange results in even a relatively simple solve.  I'd recommend analysing without a hierarchy to test this - also having a hierarchy seems counter-intuitive if your only question is which is the shortest/fastest route.

from:

https://desktop.arcgis.com/en/arcmap/latest/extensions/network-analyst/network-analysis-with-hierarc...

Using hierarchy in network analysis

It makes more sense to use a time-based attribute as impedance when performing a hierarchical network analysis. If the impedance is not based on time, using a hierarchy may not produce realistic results. For analyses that don't minimize time, consider solving without using the hierarchy