SRC_RTG_EXPIRY_TIME源路由表超时时间宏定义应该怎么设置？

ti官方400+节点实验中有这样一段话：
[size=150%]If the concentrator is memory constraint, it is very important to note the source route expiry timeout (SRC_RTG_EXPIRY_TIME) value should be such that no more than (MAX_RTC_SRC_ENTRIES) devices reporting within this interval. In this case concentrator should be able to store the paths back to all the nodes as they report data (even if the concentrator does not have memory to store path to all devices) as expired routes will be replaced with new routes and the network should not see broadcast route request storms originating from the concentrator which can cause the network throughput and reliability to go down significantly.
这段话没有理解透彻，到底SRC_RTG_EXPIRY_TIME这个源路由表超时时间宏定义应该怎么设置，特别是标注红色字体这句，真心没有翻译明白，希望大神解答下；
MAX_RTC_SRC_ENTRIES这个宏中标注红色的C应该是G，即源路由表的最大个数。