diff --git a/mlpstorage_py/submission_checker/checks/training_checks.py b/mlpstorage_py/submission_checker/checks/training_checks.py
index 92cd7062..b24e1936 100644
--- a/mlpstorage_py/submission_checker/checks/training_checks.py
+++ b/mlpstorage_py/submission_checker/checks/training_checks.py
@@ -193,14 +193,24 @@ def recalculate_dataset_size(self):
                 min_samples_memory = (total_host_memory * HOST_MEMORY_MULTIPLIER *
                                     1024 * 1024 * 1024 / record_length)
 
-                # Take max of both constraints. The memory-derived branch is
-                # a float, so ceil (not floor/int cast) to stay in lockstep
-                # with datagen (rules/utils.py) — otherwise a dataset sized
-                # to the floor passes runtime but fails this check by a
-                # single file, and the message would read "N < N" because
-                # int(min_total_files) truncates the float.
+                # v3.0-round grandfather: ceil-minus-one, not ceil. Datasets
+                # generated before the floor->ceil datagen alignment (mlpstorage
+                # <3.0.43, commit f9d414d) were sized with integer floor division
+                # in rules/utils.py, so a ceil threshold here rejects a valid
+                # pre-alignment dataset by exactly one file (e.g. 4710038 <
+                # 4710039). We can't just floor this expression: datagen floored
+                # via integer `//` while this check recomputes the same formula
+                # as a float chain, so float drift can push floor() one above the
+                # recorded count and still reject. `ceil-1` equals floor() for
+                # non-integer ratios and grants one extra file of slack exactly at
+                # the integer boundary where that drift bites — absorbing the
+                # bounded <=1-file divergence. Stays int-vs-int (no "N < N"
+                # display bug) and still rejects genuinely undersized runs (short
+                # by >1 file). REVERT to plain math.ceil once the v3.0 round
+                # closes — post-alignment datagen ceils, so newer datasets pass
+                # either way. See memory grandfather-floor-3.1.2-revert.
                 min_samples = max(min_samples_steps, min_samples_memory)
-                min_total_files = math.ceil(min_samples / num_samples_per_file)
+                min_total_files = math.ceil(min_samples / num_samples_per_file) - 1
                 min_files_size_gb = min_samples * record_length / 1024 / 1024 / 1024
 
                 # Verify actual matches expected