Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Silicon Labs/Series1/EFM32GG12B/EFM32GG12B410F1024IL112/USB/DIEP0TSIZ#0x0
Device IN Endpoint 0 Transfer Size Register
Transfer Size
Packet Count
https://github.com/cmsis-svd/cmsis-svd-data