diff --git a/sfm/server.py b/sfm/server.py
index 077a3a5..56b4b5c 100644
--- a/sfm/server.py
+++ b/sfm/server.py
@@ -894,7 +894,7 @@ def device_event_blastware_file(
                     rectime = float(info.compliance_config.record_time or 1.0)
                 except (AttributeError, TypeError, ValueError):
                     pass
-                extra_chunks = max(1, round(rectime * 2))
+                extra_chunks = max(1, int(rectime))
                 log.info("blastware_file: rectime=%.1fs → extra_chunks=%d", rectime, extra_chunks)
                 events = client.get_events(
                     full_waveform=False,