Lewis Part II:
The transformer doesn't have a power factor, the PF comes from what it is connected to. Or, the power factor is W/VA, which is close to one for a light bulb (resistor), or close to zero for a pure capacitor or inductor (reactor). Now feeding a transformer into a PF of zero, you will get zero Watts, while a Voltmeter-Ammeter arrangement will read VAs, and plenty of them.
So, once again, since the maker of the transformer cannot control the power factor of what it is connecd to, rather than Watts, they rate the transformer in VA
instead of Watts. By the way, shen the advertise those capacitor thingies on TV that show the Amperage of a fridge going down when it is connected in circuit, if you had a Wattmeter connected in the circuit it would show very little, if any, change. You are making the power company happy bu raising the power factor (canceling out some of the inductive load with capacitors) but the kiloWATTmeter on the side of the house doesn't know about it, as the field of that thing (Volts) is at zero when the current (Amps) is at max. A Voltmeter (VA) and a Wattmeter (Watts) only read the same with light bulbs, electric blankets, toasters, ovens, etc,.
Sometime, you will see capacitors on top off a pole, with a timer down on the side of the pole. This means there is a factory or something with a lot of motors, etc. nearby and they correct the power factor while the factory is in operation (hence the timer).
Lewis

::::Here are the exact specifications:
::::120v 60hz / 17v 2.5va Smallwood BTX-1389 class 2
:::
:::P=ExI, so I=P/E, or I=2.5/17, or I=.147 A, or 147mA of current.
:::
:::Lewis