diff --git a/src/twomartens/masterthesis/aae/train.py b/src/twomartens/masterthesis/aae/train.py
index 0e0e6fe..0d0f244 100644
--- a/src/twomartens/masterthesis/aae/train.py
+++ b/src/twomartens/masterthesis/aae/train.py
@@ -58,12 +58,12 @@ def train_mnist(folding_id: int, inlier_classes: Sequence[int], total_classes: i
     mnist_valid = []
     
     for i in range(folds):
-        if i != folding_id:
+        if i != folding_id:  # exclude testing fold, representing 20% of each class
             with open('data/data_fold_%d.pkl' % i, 'rb') as pkl:
                 fold = pickle.load(pkl)
-            if len(mnist_valid) == 0:
+            if len(mnist_valid) == 0:  # single out one fold, comprising 20% of each class
                 mnist_valid = fold
-            else:
+            else:  # form train set from remaining folds, comprising 60% of each class
                 mnist_train += fold
     
     outlier_classes = []