Well, I could be you battery is dying. This is mine output which has
time to empty and my battery capacity are going down also (last time I
check, it was more than 60%.
present: yes
state: discharging
time to empty: 2.0 hours
percentage: 90%
capacity: 54.4318%
technology: lithium-ion
You might want to check /etc/UPower/UPower.conf file. Either using
UsePercentageForPolicy=true or UsePercentageForPolicy=false
I once wrote a note about this to myself about this
https://robbinespu.github.io/eng/2018/03/16/Setting_power_management_when...
p/s : My laptop are 6 years old.