It is written there
INPUT: 100-240V ~ 2.5A
OUTPUT: 20V 8.5A
I believe for AC Input they mean Root mean square voltage/current.
for output it is clear ($W=U \cdot I$) or $170W = 20V \cdot 8.5A$.
But I do not understand it for input. If it is working for minimal input voltage 100V, then minimum power should be $100V \cdot 2.5A = 250W$ or for 240V $240V \cdot 2.5A = 600W$.
Even for minimum 100V power is 250W, then where the difference between input and output 250W-170W=80W goes? I mean from energy conservation law output power should be equal to input power minus losses or $Output Power = Input Power \times Energy Conversion Efficiency$
Does that mean my adapter has 68% efficiency on 100V and 28% on 240V? I believe Energy Conversion Efficiency for modern AC/DC adapters should be quite high around 80-90% or I am wrong? This adapter is quite new. I bought it in January 2020 and it was a new one and a new Laptop model.
My question is: Why there is so big difference in input and output power or what is wrong with my calculations?