Issues with compressing

[dototodo23-lang]

After the initial compression, Total War Warhammer III was compressed to ~66 gigabytes. But after decompressing, the game now compresses to a maximum of 4 gigabytes of its original size. How can I fix this?

[dnlck84]

Ensure you've used CompactGUI ONLY after ensuring none of the folders or files are compressed using the default (different, incompatible) Windows file/folder compression.

I can suggest that because I know that can cause problems, but I don't know what is intended by "[...] a maximum of 4 gigabytes of its original size."