These are two seperate things, but I can see the confusion.
On one hand you do have what @THALL has stated with the percentage value sometimes not going as low as expected, the batteries operation is based on the actual voltage readings of the cells themselves. The percentage figure is a calibrated figure from the point of the state of charge calibration thats ran, after a number of cycles the percentage to cell voltage readings is becoming unaligned, overtime the % will again re-align itself so it is not service affecting, but a visual display error with the percentage, however as the throughput is based on the cells going to their upper and lower voltage limits however it does not affect how much you can actually put in/out the battery.
The second thing in relation to the power reserve @mjkelly5a is specific to the setting currently locked in the app, this is where customers would typically change the batteries reserve limits to 50% for instance if they know a storm is in the area and are potentially liable for a power cut, that setting is then set to reserve the battery so under normal operation it will not discharge below X value. This works in the new portal on the hybrids from my testing but I had seen that the AC coupled was in some cases going lower than the % figure that was stated, that is why we're working on a fix for that.