Yeah, we need some more information about what exactly you're wearing. There are different types of armor bonuses, and not all of them stack with each other. (For instance, wearing Bracers of Armor does not stack if you're already wearing armor in your body slot.)
I think that the 'armor class' you've pointed at in the first screen is actually the 'armor class bonus' coming from abilities scores.
In the English version is also called 'Armor Class' in both instances (i.e. the actual armor class and the bonus,) but that second one is always fixed at the value provided by your DEX score.
EDIT: I cannot give a meaningful comparisson screenshot, since I have installed an UI mod in all my games, but here's how it looks in the English version for me:
EDIT2: added spoiler tags so the pic doesn't show up by default
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http://www.noelshack.com/2019-30-6-1564204827-bg2.jpg
In the English version is also called 'Armor Class' in both instances (i.e. the actual armor class and the bonus,) but that second one is always fixed at the value provided by your DEX score.
EDIT: I cannot give a meaningful comparisson screenshot, since I have installed an UI mod in all my games, but here's how it looks in the English version for me:
EDIT2: added spoiler tags so the pic doesn't show up by default