Does the numbering belong to the same list?
Did you define paragraph styles?
Are these paragraphs part of the main story or are the in not connected text frames?
Thanks for your reply, Willi. Yes, the paragraph style called for a list called "Figures". Yes, I used the same style, yet the system jumped from 4 to 2. They are part of the same story and are in the same file.
In the mean time I defined a new style based on a new list called "Platen" and I changed the styles of the old paragraphs int the new and that solved the problem.
Although I have solved my problem, I am available to continue with experiments if you want to debug InDesign.
In my last preflight I came accross a hidden textblock with the Figures style and probably with a rest of the mumbering, because it had the number 1.
Sorry for the confusion.