The following code produces what appears to be two milestones rather than one milestone after a one-day task. Single time unit duration tasks should be visually distinct from milestones (which are zero-time events.)
@startgantt
[Init Counters] as [cfg_ctr] lasts 4 days
[Init Decay Ctr] as [cfg_dec] lasts 1 days
[cfg_ctr] -> [cfg_dec]
[Init Complete] happens at [cfg_dec]'s end
@endgantt