[color:"orange"]4434/5600 (never got that part actually :s )[/color]
The weight of everything the DK is carrying is 4434 units, while his maximum capacity is 5600, so he is at 79% of the weight limit. IIRC the point where characters becomes encumbered is 75% of the maximum.
The maximum weight capacity is the most weight you can carry and still be able to walk around (in the game this is directly proportional to the character's strength). The encumbrance limit is the most weight you can carry and still be able to run around. Realistically, the latter limit is going to be lower than the former, and the game simplifies it to 75%.
With the patch installed, characters can hold items past their maximum weight capacity, but then can not move at all (this make the summoning dolls even better as mules to carry excess stuff).
[color:"orange"]while I was dropping things he was suddenly not encumbered anymore, but it's not like I dropped anything special, just all items like food, keys, gems, gold... all charms, when I started on the potions, I dropped a strength potion and he wasn't encumbered anymore[/color]
Gold and charms shouldn't have made a difference, since they don't have weight. Food and potions are stackable, so after awhile their weight can start to add up. That last potion may just have been enough to get you down under 75% (IIRC) of your maximum capacity.
[color:"orange"]I put my response within your answer, but I wasn't able to put a colour on it :s[/color]
If your browser doesn't insert the colour tags when you click on one of the colours in the 'Font color' section under the text box, you can manually type in the tags and type the text between them;
[ color:orange]text[ /color] -- spaces added after the '['s so it stays as plain text
or put quote tags around individual sentences/paragraphs.