When You start amule and the upload queue is empty and a first client starts downloading, then for the first times the "waiting" time is 0 s. But when more clients connect, but the number of clients is less than upload bandwidth divided through the slot bandwidth, meaning no client has to wait for beeing served after last chunk completed, suddenly the "waited" value for clients jumps up to several minutes. But no client waited minutes, maybe a few seconds. Maybe the downloading time is interpreted as waiting time??
aMule 2.2.6