First off I would personally learn the the machine in the Smart Screen.
Later you will clearly learn to pick up on the Cursor Flutter or Skips which are tell-tale of deeper coins etc. Even Nickels have their own place and movement. I never resort to VDI numbers.
My settings are: Manual Sens. any where from 23+ depending on the site, Fast On/Deep Off, Threshold barely Audible, Channel 11 preferable, Ferrous Tones (yes Ferrous for 12 years now), Gain 7, IM set at -12.
Those are the major settings but, there are others as well.
For you I would personally just stay in the Preset Coin program for a while until you learn the machine or you will be overwhelmed by the sounds opened up in -12 IM. Note: the preset Coin program is default Conductive Tones.
But, since you asked for VDI numbers here is a link that gives you VDI numbers.
VDI Reference Numbers
Whichever you choose be it Ferrous or Conductive with similar settings above stick with it and hunt and you will be on your way to success.
Hope I was of some help.
This post will probably get moved to the Explorer Classroom.