The percent here represent the percent contribution of the particular ROUTER to the total count of events. So if the index=xyz sourcetype=JUNIPER LSP_DOWN returns N events, routerx has 1887 counts out of it and 1887 is 11.08 percent of N.
If you're seeing a discrepancy in count, it may be due to the fact that ROUTER field is not available in all the events. I would suggest to run this and compare the result (ensures to select only the events which has field ROUTER available)
index=xyz sourcetype=JUNIPER ROUTER=* LSP_DOWN | top limit=10 ROUTER
Holy cow all this time I've been using top limit incorrectly 😞 Thank you for the info. My mistake being a newbie is relying solely on an example shown in splunk documentation without analyzing the data.