This sets the priority of a system reference clock source: a lower numeric value takes precedence over a higher one as long as that lower-priority-number source remains available, and the system automatically selects among sources tied at the lowest available priority value. Setting nodeRefclocksrcPriority to 1 on the most reliable external clock source, such as a GPS-derived reference, ensures the switch prefers it over less-precise line-recovered clocks whenever it's up.