why is level0 changes every time I compile?

hi everyone

I plan to make patch for android game.
so my plan is simple. build game in Unity with 'split application binary', so its output is apk+obb.
assume that obb is only data and apk is just Unity call process, I have to release obb file only.
but not like my guess. it's not working, even if build same project and replace only obb file.
turned out 'assets\bin\Data\level0' is always changes. and logcat says "Level '' (1) couldn't be loaded because it has not been added to the build settings.".
so I can't release obb file only.
does anyone know why this 'level0' changes everytime? or at lease how to fix its binary output?
only changes is 'level0' in obb file and 'settings.xml' in apk.

<?xml version="1.0" encoding="UTF-8"?>
<settings>
<integer name="gles_mode">2</integer>
<integer name="splash_mode">0</integer>
<bool name="hide_status_bar">True</bool>
<bool name="32bit_display">True</bool>
<bool name="24bit_depth">False</bool>
<integer name="default_aa">0</integer>
<bool name="useObb">True</bool>
<bool name="d46b16d639ea621d5a4d08eba9d7faec">True</bool>
</settings>

is this bold name relate with level0?

 

this is damn old but it probably is related to it