Watt-Hours are unambiguous units of energy, Amp hours are ambiguous without knowing the voltage.
since you said mAh (milliamp-hours), I'm thinking you are talking about phone batteries which are typically in the 3.3-3.6V range depending on the chemistry, then 1000mAh would be 3.3-3.6Wh.
As a comparison the Dell XPS 13 has a 52Wh battery, so it's not a very big battery. 49Wh is what the new MacBook Air has, but the Air has a much lower power CPU.
For reference the LG Gram 15 has a 72Whr battery at 1.1kg. The current champ in 'battery size to weight ratio'. Most ultraportables have a 50-60Whr battery at around 1.3kg.
I think 3.64 lbs (1.65kg) is perfectly acceptable for a 15" laptop, not the lightest but also not the heaviest.
However 49Wh is on the low end for this size laptop imho. Granted it isn't having to put a HiDPI screen and hopefully the Ryzen is more energy efficient than Intel but I doubt it is going to be a show stopper in the battery life department.
Not huge; same as a MacBook Air (a much lighter laptop). For something this size you'd generally expect more.