Keep in mind you will get the best mileage at slower speeds using PAS 1 and applying as much pedal pressure as possible. Your weight, the gear you carry, the slope, riding surface , tire pressure and the wind conditions will also factor in. As Eu224 mentioned above, 18 - 20 watt hours per mile is a good estimate for us older folk but the average is closer to 14 - 15.
For example, I have a platinum Interceptor which uses the same 10 speed drive train as the Platinum Boomerang. It also uses the same battery format except in my case, it's the older 52V 15 AH model. I'm 74, and weigh 255. I carry around 30 pounds of gear and the best I've been able to do is 54 miles on a single charge. This was done on a calm day on smooth level blacktop using PAS 1 and applying moderate pedal effort mostly in 8th gear with the speed at 12 MPH. Again, my battery is the 52V, 15 AH model which puts me in the 14 - 15 watt hours per mile range. Using the above criteria, 60 miles per charge should be possible with the new 17.5 AH battery.
It should be noted however that I don't usually ride to get the best mileage. I ride mostly for enjoyment and moderate exercise. The above scenario is a bit more strenuous than I prefer to do on a regular basis. On average, with the 15 AH battery, I get approximately 36 miles per charge. That puts me in the 20 watt hours per mile range.
I deal with range anxiety by carrying a spare battery. I don't always need it but it's nice to have it when I do.