Fix wrong interval unit when computing jitter

scripts/txtime_stats.py

@@ -54,7 +54,7 @@ def compute_offsets_stats(file_path, interval):
 
             if i > 0:
                 val = arrival_tstamp - prev_tstamp
-                jitter = (val - interval) / 1000
+                jitter = (val - interval * 1000) / 1000
                 histogram_index = int(1000 + jitter)
                 if histogram_index < 0 or histogram_index > 2000:
                     print("jitter too high: {}\n".format(jitter))