Some of the cell meters lose accuracy especially in the % function.
% remaining isn't a very firm value to begin with. From my reading, the % remaining is related to the cell voltage and calculated off of an algorithm or known curve. There are more than one set of values/curves and they don't always agree.
A friend with low % remaining (18-19%) said that his replacement mah was about 1650. That doesn't make sense. Even my well used Zippy batteries have 2500 mah. If I use 1650 mah by replacement, I should have about 33% remaining. Interesting that when I put the pack on my Powerlab 6 after a flight, he had about 33% remaining, and his meter said 18%. Of course either my charger and/or his meter could be wrong, but the % remaining or % used should agree with what is in a full pack meaning a % of 2500 - 2800 mah depending on the age and use of the pack. Try a friends meter, or depend on mah refilled/estimated full pack mah for the actual % used.
For reference, I will have about 20% remaining at 3.75V at the end of a flight with several minutes rest, and that % is falling fast below that voltage.
Hope that makes sense and helps.