I stopped by an e-bike dealer yesterday and test drove three different types of AOWA bikes. Their prices are incredibly reasonable! I'm planning to purchase one very soon. My question now is:

Which one? I've narrowed my decision down to two of them. One is a 48v, 12 amp that can travel 15-30 miles per charge. The other is a 48v, 20 amp that can travel up to 40 miles per charge. What does it mean by 15-30 miles? Does that mean that if it's charged only halfway, it will take me 15 miles and fully charged it will take me 30 miles? Is there give/take on that? I want to be sure so that I know what I'm putting my money into. But I'm buying one of the two for sure!