[tokenmasterhk]

High compression ratio is depends on how many available ram of the PC. The higher the ram, the smaller the file size.  But my computer is not a monster, otherwise I can further reduce the file size.

Yeah, but if I pick 9-Ultra it sets default values that doesn't achieve that big compression ratio as you have
So you set the values manually, right? Can you share your manual settings? Dictionary size, Word size, etc

This is the setting I used. I captured the setting from laptop for information.

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From 7zip's help:

LZMA2 Default compression method of 7z format. LZMA2 is LZMA-based compression method. It provides better multithreading support than LZMA. But compression ratio can be worse in some cases. For best compression ratio with LZMA2 use 1 or 2 CPU threads. If you use LZMA2 with more than 2 threads, 7-zip splits data to chunks and compresses these chunks independently (2 threads per each chunk).

From 7z's help, it is the recommended setting. But I used 3 CPU threads, same file size is output but faster.

I tired 4 CPU threads, the output file size is bigger.