Microsoft has rolled out a new Windows 10 Mobile cumulative build for Windows Insiders on the fast ring who are currently running the Creators Update. While there’s no changelog up yet, we can assume this fixes a few bugs here and there and smooths out the already smooth experience.
The version number is 10.0.15063.138. While Microsoft uses the nomenclature “Windows 10 Version Update XXX for arm-based Phone devices”, this probably doesn’t mean anything at this stage (if it does, it’ll be revealed at Build).
That being said, you can download the new update from settings > Update and Security on your Windows 10 Phone.