What does the BJWFlate -s option do?

Here's the usage information:

- Option -s: Number of splits. Default: 120. Allowed: 3-8192.

I don't understand what splits are.

The default is 120, in your sample ZipMax ini, you have -s64

How did you decide on 64?

Is there any kind of rule of thumb like...

less splits yields smaller file but slower compression
more splits yields bigger files but faster compression

<*crossing fingers*>

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