This article is written to show the timeline that MIST takes to reflect the changes as made on a Junos Switch - EX2300 in this case.
Mist Claim code to connect switch to portal takes: 1 min.
IP address for the ZTP was seen on the portal in: around 10-12 mins
Mist management config through MIST when applied reflected on the portal in: 15 mins
New member to the existing VC using MIST: took around 15 mins.
This is the expected time taken.
Attached email from MIST Engineering team. This is as expected timeline,
With newer platforms the time taken may be less.