diff --git a/data.sql b/data.sql
index 4d56d67..b6f03fa 100644
--- a/data.sql
+++ b/data.sql
@@ -904,4 +904,4 @@ UNLOCK TABLES;
 -- Dump completed on 2024-11-24 22:58:20
 
 -- Persist per-indicator warning direction after seed inserts.
-ALTER TABLE `fa_testing_params` ADD COLUMN `direction` varchar(5) DEFAULT NULL COMMENT '预警方向：upper高值预警、lower低值预警';
+ALTER TABLE `fa_testing_params` ADD COLUMN `direction` varchar(5) DEFAULT NULL COMMENT '指标偏好：upper越小越好（高值预警）、lower越大越好（低值预警）';
diff --git a/public/screen/js/grain_monitor_core.js b/public/screen/js/grain_monitor_core.js
index 1c43e6a..4db298c 100644
--- a/public/screen/js/grain_monitor_core.js
+++ b/public/screen/js/grain_monitor_core.js
@@ -1379,7 +1379,7 @@ export function buildForecastCompareChartOption(grainType, currentItems = [], fu
     const delta = current !== null && future !== null ? Number((future - current).toFixed(2)) : null;
     return {...f, current, future, unit, scale, delta};
   });
-  const datum = (r, value) => ({value: value === null ? null : value / r.scale * 100, rawValue: value, unit: r.unit});
+  const datum = (r, value) => ({value: value === null ? 0 : value / r.scale * 100, rawValue: value, unit: r.unit});
   return { animationDuration: 350,
     aria: {enabled: true, description: '每个指标独立对比当前实测与未来预测，柱长仅可在同一指标内比较。'},
     tooltip: {...forecastTooltip, axisPointer: {type: 'shadow', shadowStyle: {color: '#94adc808'}}, formatter: params => {