This is something you'll notice with devices that use small batteries if the manufacturer didn't program 100% to persist longer.
The remote will charge up, stop charging, drain a bit and then eventually start again. Since the battery is 410 mAh it only needs to drop 4.1 mAh to read 99%. Like mentioned, unplugging it and plugging it back in will sometimes restart the charging and get you to 100%.
On devices like laptops, smartphones, and most anything with charging circuitry and software to display battery % manufacturers will program 100% for a larger mAh drop. Using my MBP for example.
It says fully charged, meter reads 100% however if you do the math the battery is actually at 97%.