General instruction is to place media beneath the calibration platform and adjust height until there is just a slight drag when pulling the media out from beneath.
More importantly the i1Pro MUST remain in contact over the entire measured surface. If your deck has slight low points, ensure that the head remains in contact in these areas. Gently move the reading head back and forth over the media to verify contact.
Slightly increased drag in the high spots will not affect measurement data and the teflon foot will protect the media.