KEEP_LOGS_DAYS value

- Then what logs point to 28 days (default value)?

- Is this the value of keep logs days that is changed to 60 days in my master server host properties ----> Clean-up ----> Keep logs value?

The 28 day default value for "host properties ----> Clean-up ----> Keep logs " is for ALL process logs, unified and legacy logs under netbackup/logs (if you enable the directory names for those processes)  except for the user_ops logs which is controlled by the KEEP_LOGS_DAYS (which is 3 days)

you have increased your "Clean-up -> Keep Logs"  to 60 days, so you will retain 60 days of legacy and unified logs. I personally would leave it at 28 days, but it you have the space to keep 60 days worth of logs and that is your requirement then that is your decision to make.