Dave, I know the specs say 7.7 gallons but I actually ran out of gas once (faulty sensor in lower tank) and coasted into a gas station. I put her on the center stand and filled it to the top.... 7.4 gallons was all I could squeeze into her. So, there must be 0.3 gallons of the listed 7.7 that is unusable.
The whole problem with fuel level is the sensors will not be accurate if you don't take the level down after about 5 fills.
I noticed the reserve feature started tripping earlier and earlier, so I tested it.
I took a Rotopax can off another bike and stuck it in my top box when I was able to time the reserve to kick on when I was home.
When I first got the bike I measured around 340 miles before the reserve light went on.
Then it started kicking on around 300 miles.
Granted I started riding a lot more aggressively, but that was a big drop.
I took off and went for a ride with the spare gas and the reserve was showing 42 miles.
I didn't ride out the tank because I didn't have time but it stayed at 42 mile range for several miles before dropping to 41 mile range.
I rode a 20 mile loop but it still showed 35 miles.
I called the dealer's service dept the next day and was told the level sensor "recalibrates" itself and if never run low it will have errors indicating less gas than what is actually present.
They said the best practice is to run it partway down on reserve.
I've noticed about every 5 or 6 tanks the levels seem wonky.
That reserve flash and miles left feature is automatic on my bike.
Don't know if that's a setting, I got mine with 1500 miles on it in mint condition.