Charts and air tests are useful information, but those numbers change from targets in the ground, depending on ground mineralization, iron & trash levels, how long the item has been in the ground, and size of buried objects. The VDI numbers have as much to do with size of a target as they do the type of metal, perhaps more so.
You didn't say where you hunt, but trust the factory presets. They were designed by experts in the field from several countries. If you're in a park or yard, Park 1 will hit coins & silver hard and most normal size gold jewelry. Park 2 will favor small gold but will hit everything else too. In farm fields or large areas of previous habitation, Field 1 & 2 are very similar to the Park modes but has coke notched out. On a Beach, use the Beach modes. In the gold fields, use the gold modes.
US coins will hit between 12-15 for nickels, and 19-32 for all other coins. Gold jewelry can be anywhere from -2 to 25 depending on size, shape, & thickness. Silver jewelry can be all over the map too depending on size, shape, and thickness but will generally be 5-38.
So don't rely too much on numbers and listen to the sounds. The sounds reveal much more than the numbers do. If it sounds good, just dig it! HTH
