Issue
The Unity help is a bit misleading in one section. It does not explain the high byte, However in the section Using the R_NTPC Block for Time Synchronization it explains it fully.

Product Line
EcoStruxure Control Expert (former Unity Pro)

Environment
Unity Pro v8.0

Resolution​​​​​

In the R_NTPC function block the Status output is an integer. The high byte indicates that the NOE received an acceptable time value. The low byte indicates the date and time have been updated so a value of 247 would mean the result was successful.