XPS 15 9550 Battery Charge decreasing noticeably

I've been using PXS 15 9550 for a while (around 6 months) now with Arch Linux.

One thing I noticed from the output of "tlp stat" is that the battery charge keeps decreasing. I highest I remember is around. The output is:

+++ Battery Status /sys/class/power_supply/BAT0/manufacturer = Samsung SDI /sys/class/power_supply/BAT0/model_name = DELL M7R965A /sys/class/power_supply/BAT0/cycle_count = (not supported) /sys/class/power_supply/BAT0/charge_full_design = 4912 [mAh] /sys/class/power_supply/BAT0/charge_full = 4122 [mAh] /sys/class/power_supply/BAT0/charge_now = 2613 [mAh] /sys/class/power_supply/BAT0/current_now = 2063 [mA] /sys/class/power_supply/BAT0/status = Charging

I do use the battery frequently, but not with terrible habit (depleting it, leaving it depleted, etc). Still, you can see that the full charge is significantly lower than the design full charge.

What can I do about this?