The update is exclusive to China only. The update is rolling out via OTA (Over the Air) to the Realme C17. So, it may some days to reach your smartphone. Alternatively, check the update status manually by heading to Settings -> Software update. This is a major bug fix update which addresses various bugs which were being reported after the previous update. It also promises to improve system stability and performance.

Changelog

Security Android security patch: December 2020 System Partial fixes on known issues and improved system stability

Via

 RMX2101PU 11 A 27  Realme C17 gets December 2020 security patch - 24