Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Silicon Labs/Series1/EFM32GG11B/EFM32GG11B820F2048IQ100/ETH/TSUTIMERMSBSEC#0x0
1588 Timer Seconds Register 47:32
MSB 16 bits of seconds timer count.
https://github.com/cmsis-svd/cmsis-svd-data