Are you guys talking about the same thing?
On the left are the remaining battery power bars whereas the right of the display are the load bars. Since there are 4 bars in each case, we assume each bar represents 25%. So the moment it goes onto battery power the first battery power bar dims, indicating 25% used (more accurately, 25% is in process of being used), hence leaving at least 75% of total battery capacity remaining. Only when it has used over 25% of the battery capacity will it dim the 2nd bar. Hence, the moment the third bar dims you have used 50% of the batteries stored power. That's when you want to shutoff the invertor to protect the battery.