Update README.md

README.md

@@ -89,6 +89,8 @@ The `ssl4eo_s12_nol.zip` contains the 103,793 DW noisy mask quadruples paired fo
 
 The `ssl4eo_s12_dw.zip` and `ssl4eo_s12_osm.zip` contain the training and test splits for the two curated downstream datasets. 
 
+The ground-truth mask key for the DW test split is `lulc` (the second layer).
+
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 ## Dataset Card Contact