Changing the tempo mode without changing the actual tempo (2000 Nexus)

I might be wrong here but I played on CDJs in a club once where I noticed that when I changed the tempo mode, the tempo itself didn't change until I started moving the slider. I'm trying to google the feature to no success so I'm actually beginning to doubt my memory.

Anyway, I recently got a pair of CDJ 2000 Nexus players for home practice and it would be really nice to learn how to turn this feature on, both for my home use and for my future gigs.

Any idea how to do this?