diff --git a/screening/source/core-plugins/cellomics/1/dss/drop-boxes/cellomics-dropbox/cellomics-dropbox.py b/screening/source/core-plugins/cellomics/1/dss/drop-boxes/cellomics-dropbox/cellomics-dropbox.py
index 0a6fb23f902480c1ab43bb48e796cffde0c555b2..54d42dccb825182bf1d6fbd4636a97c6fd77bc59 100644
--- a/screening/source/core-plugins/cellomics/1/dss/drop-boxes/cellomics-dropbox/cellomics-dropbox.py
+++ b/screening/source/core-plugins/cellomics/1/dss/drop-boxes/cellomics-dropbox/cellomics-dropbox.py
@@ -75,7 +75,7 @@ class MyImageDataSetConfig(SimpleImageDataConfig):
         return image_tokens
     
     def getTileGeometry(self, imageTokens, maxTileNumber):
-        return Geometry.createFromRowColDimensions(maxTileNumber / 3, 3)    
+        return Geometry.createFromRowColDimensions((maxTileNumber - 1) / 3 + 1, 3)    
  
 if incoming.isDirectory():
     imageDataset = MyImageDataSetConfig()