So these are the build stages.
https://g30.bimmerpost.com/forums/sh....php?t=1380961
If it's gone to build it'll likely be 5100. Mine went from 5100->9000 in 4 days but sat at 5055 for 2 weeks. They're pretty quick once they start.
If you have your BMW order number (starts with a 4, 7 digits long) you can use LiveChat on the BMW website to talk to the Genius folks and they'll tell you the build status code. To find LiveChat go to Build (any kind of model) and you'll see it at the bottom right. It doesn't offer LiveChat on iPhone/iPad but is fine on my iMac and also Windows 10 work laptop.
If you've not seen it then this video shows the G20 production process, pretty fascinating, although they don't show the interior construction...