Since it's public now, I can confirm that the reports about 55 achievements/trophies for GTA VI are accurate. All 55 entries (IDs 1–54 + 1000) are already configured in the Xbox API and currently locked behind sandbox.
#gta6#GTAVI
Grand Theft Auto VI Xbox Series X|S download sizes have officially updated in Microsoft's DisplayCatalog API.
Global build:209.86 GiB / 225.34 GB (225,336,053,760 bytes)
Japan build (separate regional package):208.74 GiB / 224.14 GB (224,136,269,824 bytes) #GTA6