That is normal.
Battery Management.
How battery health management helps
The battery health management feature in macOS 10.15.5 is designed to improve your battery's lifespan by reducing the rate at which it chemically ages. The feature does this by monitoring your battery's temperature history and its charging patterns.
Based on the measurements that it collects, battery health management may reduce your battery's maximum charge when in this mode. This happens as needed to ensure that your battery charges to a level that's optimized for your usage—reducing wear on the battery, and slowing its chemical aging. Battery health management also uses the measurements to calculate when your battery needs service.
https://support.apple.com/en-us/HT211094?cid=mc-ols-energy_saver-article_ht211094-macos_ui-04022020
Related:
Monitor your Mac notebook computer’s battery
If your Mac battery won’t charge
If your Mac battery runs out of charge quickly
If your Mac battery status is “Not Charging”
https://support.apple.com/guide/mac-help/if-your-battery-wont-charge-completely-mchlbfb7e12a/mac
