On Rebalancing, when start the garbage collected?

In this page,
https://www.cockroachlabs.com/docs/stable/training/cluster-startup-and-scaling.html

they said,
" Range replicas rebalance to fill available space from new node.
(next page)
Old replicas are garbage collected."

So, I wonder when start the garbage collect on old replicas?
Is on rebalancing? or After rebalancing completed?

Hey @yeri,

Old replicas will be garbage collected almost immediately once rebalancing is complete.

Thanks,

Ron