Lower ferrous # are only 0 to 9 there are no negative numbers . The nox does use negative numbers unlike the manticore there are no negative numbers in the settings for the Minelab Manticore’s Ferrous Limits.Unlike older detectors (such as the Minelab Equinox or various Whites machines) that used negative numbers like -1 to -9 to represent iron, Minelab completely redesigned the interface for the Manticore.How the Manticore Handles Iron Instead of Negative Numbers0 to 99 Scale: The Target ID (TDI) numbers on the Manticore are strictly positive, ranging from 0 to 99.The 2D ID Map: Instead of relying on a negative sign to show iron, the Manticore uses a vertical Y-axis on its 2D screen map. Ferrous targets are indicated visually by how far they deviate up or down from the clean, white center line.The Ferrous Settings: When adjusting the upper or lower limits themselves, you modify them using positive integers (0 to 9 for the lower limits, and 0 to 14 or 25 for the upper limits, depending on the software version).If you see a target flash on your screen, you will know it is iron if the visual dot drops into the lower gray shadow area or climbs into the upper gray shadow area, regardless of the positive number showing on the screen. sube