2.2 stable b can't read the Texture2D file size in 2018.2.20f1 Unity3d.
In 2017.4.2f2 it was able to read accurately.
The target game is iDOL M@STER Cinderella Girls.
upload the sample file.
https://mega.nz/#!Km4RkKiC!fmlOmXj-B8zI56ZdYVnEEr4pKeqpvTz9zQQciNBVzHM