Use XP per hour, not a perfect activity count
Quest rewards, mining, building, traps and group play produce very different experience. For a useful estimate, measure one normal hour in your world and enter that rate. The separate activity field is best for a repeatable task such as a quest tier, upgrade session or known kill.
Why the level 60 clamp matters
The experience required for each level stops increasing after the configured clamp. Long-range estimates therefore should not keep compounding forever, which is a common error in older calculators.