The base-level meaning of "Ah" (at times it might appear ... it's an indicator of roughly how long a given battery can maintain an output of at least 10.5 volts while in 80-degree temperatures ...

The included rechargeable 10 Ah lithium-ion battery pack delivers 4.5 hours of illumination at full power, but can also be dimmed to extend use time to up to 40 hours on a single charge.