What does an fping output like [<-x.y.z.w]x.y.t.m mean?

Trying to get an inventory of active devices on a newly acquired network, using $ fping -gas network/mask, and some of the results come back in the form of $subj (e.g. [<-10.1.4.2]10.1.4.3). I thought of these being some sort of HSRP/VRRP info (have not received diagrams or devices config yet), but some of these come back "far distanced", vs a normal redundancy config (where one would expect x-1, x, x+1?!?), e.g. [<- 10.1.5.10]10.1.3.255, which looks odd ...