The wattage on the box is only an upper limit. Fast charging requires the device, charger and cable to support a compatible protocol and current; a multi-port model also divides its total output among connected devices.
Compare a power bank by watt-hours, maximum output per port, simultaneous-charging allocation and recharge input. A milliamp-hour figure without voltage and conversion losses does not show how many full charges a particular device will receive.
Anker suits buyers prepared to match a phone, laptop or monitor requirements to the accessory specification. Charging requires the right connector and protocol; a dock additionally needs operating-system, display-output, bandwidth and power-pass-through checks.