Mode Z Default?

I've been using a bandwidth monitor to watch my data for the past few days and today I tested it with SamrtFTP. I downloaded around 11gb of data (mostly videos). However, the monitor only showed having downloaded around 7gb.

I've since found out about Mode Z compression. Under the site details, its set to 'default'. Does that mean its enabled? Would it really cut that much data from the download?

Many thanks.

Yes mode Z is enabled by default. But videos can generally not be compressed much mores since they are already compressed.