Lets assume its a pretty darn high quality battery, and it does put out 10.5 ah when tested at the factory.
Chances are, that test was not a 14 amps test, but 5 or so. Because of Peukerts effect, you will not get the full 10.5 amps riding at 14 amps. ( this should be a 20-25 mph cruise) However, its entirely plausible that you would get very close to 10 ah, when its new, and perfectly balanced fully charged.
Ride slower, and you might even see the full 10.5 ah.
But,, we don't ride in labs, or get perfect charges every ride, or ride in good weather every ride. And the battery is only new for a few months. Cold costs you, but wind does too, increasing the amps you have to pull from the battery, increasing pukerts. Long term, if you can wring 9 ah from it any ride for a few years, you did good.
Cheap ass battery, you might be doing good to ever get 9 ah out of it, brand new.
And then you also want to leave some reserve in there anyway, so my old rule of thumb of one ah per mile for 36v, and .75 ah per mile for 48v, when traveling at 20-25 mph, is still valid. Hell yes you can get more when you want to, but an ah per mile is what you should count on, going fast as you can on either voltage.
And two miles per ah, if you ride slow and pedal more.
But if you bump up to 20 ah, and still pull only 14 amps continous, you will be back close to the factory test amps, and should see very close to the full amount from a good battery. Or, slow to 8 amps, to get the same thing out of the 10 ah. It also helps if the seller builds an 11 ah pack, but calls it 10 ah. Many of the better batteries will be doing this, not claiming the theoretical capacity, but the actual practical capacity you could expect in the real world.
Its all about lowering the discharge rate per cell. The lower you get it, the happier the cell is. It makes no heat discharging, which is where that ah went when you hauled ass on the small battery.
For my long rides, I loved to run 30 ah or more, and still keep the amps very low. No voltage sag under load means maximum capacity and distance. I could wring 80 miles from 30 ah of 48v that way.