A 15aH 36v battery has about 600wH in it. You can give them out slowly, in which case you have to pedal hard or go very slow, or you can give them out fast and not have to pedal so hard and/or you can go faster. Your range for a given battery will depend mainly on the ratio of pedal power to power being given by the battery. Switch the battery off and your range is infinite. Apply a tiny bit of battery power and you can go a very long way. Increase your battery power a bit further and you won't go so far. That's logical. Therefore any claims about range while you're pedalling are meaningless.
For the same bike a 15aH battery will go a bit more than 50% further than a similar 10aH battery on the same bike and pedalling the same, so if you get 50 miles on a 10aH battery, you'll get about80 miles out of a 15aH one.
if I turn my bike down to minimum assist, it draws 4watts from the battery, and I'll be able to pedal at an average of 9mph. my battery has about 800wH (round number) so it'll go for 200 hours, which means a range of 1800 miles.