What weight are you talking about, what items? I guess stats are right ingame but if you look at xp and gold, website is always right.
Checkout the weight when you put the mouse to select an item in game,
Polished gauntlets 1.2 ingame 1 on website
Sipahi Helmet 1.2 ingame 1 on website
Light Leather 4.9 ingame 4.8 website
Druzhina Elite Lamellar armor 21.4 ingame 21.3 website
Vaegir Elite armor 20.7 ingame 20.5 on the website
Shirt 0.2 ingame 0 on the website
Etc.
The weight of all items is not the same, I guess it takes the one in game? What's that?