To be fair, most laptop battery indicators are broken. I've never had a Li-Ion device that didn't exhibit a non-linearity in terms of power draw vs percentage

To be fair, most laptop battery indicators are broken. I've never had a Li-Ion device that didn't exhibit a non-linearity in terms of power draw vs percentage estimation. 100% lasts much longer than 99%, which lasts longer than 98%, down to about 92%, after which point the draw-per-percentage seems to be fairly linear. Anecdata, I know.