Update model card

README.md

@@ -60,9 +60,11 @@ repository's `docs/preprocessing.md`.
 ## Training data
 
 HiPredict was trained on the [HiPredict dataset](https://huggingface.co/datasets/ardan-S/HiPredict).
-Its patch sets are split chronologically into 70% training (81,717 sets), 10%
-validation and 20% test. The observations were processed with HiPROC 0.11.0 and
-ISIS 9.0.0.
+Its patch sets are split by date: the earliest 70% for training, the next 10%
+for validation and the last 20% for testing. The model was trained on 81,717
+sets, at a point when the record held 51 fewer patch sets than the published
+version; the same split of the published record gives 81,753 training sets.
+The observations were processed with HiPROC 0.11.0 and ISIS 9.0.0.
 
 ## Performance