Word lays out content in a logical order but it appears you don't structure your content in a regular way. Are you placing these captions inline or using floating text boxes to arrange your pages?

We can't see what is going on from a screenshot but I can see that:
1. You have Abbildung 3 and 4 in the same paragraph
2. You probably have tracked revisions and have deleted a few captions which are still 'in the document' which is probably why you skip some numbers.
3. You don't appear to have refreshed your captions. When done correctly, captions use a Seq field to provide the incrementing number and those fields need to be updated manually if their numbers don't appear correct.

I'm guessing on the strange order but if you have already updated the fields then I would be looking at where the anchors for those floating boxes are located.

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Andrew Lockton
Chrysalis Design, Melbourne Australia