ATL — running all-time low. Steps down whenever a fresh low prints.
30d / 90d / 180d / 1Y / 1.5Y — spike-from-ATL levels calibrated so each one is hit roughly once every N trading days, historically. Higher = rarer.
Circle markers (+180d, +1Y, +1.5Y) flag the first bar in each ATL cycle that touched the corresponding level.