This is like the extra storage built in to almost all Solid State Drives for computers. This storage is hidden and is used by the onboard controller to add space when some sectors of the main drive become unusable. this is done in order to keep the drive functioning at full capacity for as long as possible. It’s a hidden system and the users, rarely ever, are aware of it. This extra space only becomes active when required.

Similarly, in the case of batteries, extra battery arrays are given to help keep the battery at full capacity even if some battery banks become weak. It is only a very small amount and the user is not even aware of it; only becoming active when the system detects an issue with the main battery array. So, every EV has a similar buffer in their batteries. But in Toyota’s case that seems to be half the battery and they seem to be claiming it as “range”. 🤯🤦‍♂️