Aerospike backups

Hi, I’m trying to run incremental backups every 12 hours. For example running backup at 3:00 PM with parameters -a 2018-11-05 03:00:00 -b 2018-11-05 15:00:00 and nextday at 3 AM -a 2018-11-05 15:00:00 -b 2018-11-06 03:00:00.

My questions is till what time the backup will be taken when backup runs at 3PM does it backups from 3AM to 3PM or 3:01AM to 2:59 PM.