"Stg" and trailing underscores in task names

Hi, when dealing with the `task_name` column of `batch_task.csv` in cluster-trace-v2018, I found two anomalies:
1. Some task names contain "Stg", e.g. J10_7_9_Stg4 (belonging to job j_9395). Judging from the context, there isn't a "task 4" in this job. So what does "Stg4" mean?
2. Some task names end with underscores, e.g. J30_4_5_6_8_9_10_12_13_14_16_17_18_19_21_22_24_25_ (belonging to job j_4142). Is the trailing underscore simply redundant, or does it imply something?

Could you please answer to my questions? Thanks!