Finding the pitch and moving the listening notch are two different jobs. This step only searches. It starts as a half-octave band of noise centered near 15 kHz, where you think the tinnitus sits. Step down and step up move that whole band so the next one starts exactly where the last one ended — no overlap. Narrow tightens the width in steps: half an octave, then a quarter, an eighth, then one semitone. Widen goes back up, and it will not go wider than half an octave. At one semitone you hear a single tone instead of noise. The center slider runs from 1 kHz through 20 kHz. Match at a quiet volume. This is not a medical device.
When you lock a pitch, the notch is centered on that frequency. You do not set a separate low and high band. Each slice is a hard notch half an octave wide. Playback starts two slices below the locked pitch and walks upward, edge to edge with no overlap: two below, the center, and two above. About 30 seconds on each slice, then it loops. A slice is left out only when its top edge is too high for this device to play (or the slice sits entirely below 1 kHz). The status says so.
Volume at or just over covering the tinnitus.