Disclaimer: I know nothing about electronics or guitar amps.
(Actually, I do know one thing: that "wattage" is synonymous with "volume" when speaking about guitar amps and since watts are measured on a logarithmic scale, a 100 watt amp is only twice as loud as a 10 watt amp...I think.)
I am very confused.
My question applies to any guitar amp, but as a random example, I will use the Fender Blues Junior III amp.
According to the product description on the official Fender website (and all product descriptions of this amp online), it has 15 watts:
But, according to the plate on the back of the amp itself, it has 180 watts:
How come there are two different watts numbers with guitar amps? What does each number represent, and how can they both simultaneously represent the amp's "wattage"?