diff --git a/laborious/activities/model_metrics.py b/laborious/activities/model_metrics.py
index dce8523..3d55997 100644
--- a/laborious/activities/model_metrics.py
+++ b/laborious/activities/model_metrics.py
@@ -293,7 +293,7 @@ class ModelMetrics(SientiaMonitoring):
         metrics = input_data['metrics']
         interval_minutes = input_data['interval_minutes']
 
-        data_size = len(target_data)
+        data_size = data.shape[0]
 
         output_data = []