Similar question was already answered but I can’t retrieve it for now.
Your document was initially written with M$ Word and subsequently converted as can be seen from the numerous WWW8Num1z* character styles and the Convert * page styles. Since Word has a much less rigorous definition of its format, the conversion process did its best but this resulted in some errors and approximations.
One of these errors is the “pollution” of the chapter numbering feature where a dot is added after the number. In your case the number is “none” but this is nevertheless a (void) number. You wouldn’t have noticed it if you had a real chapter number.
To fix, open Tools>Chapter Numbering, Numbering tab and remove the After Separator in the affected levels (1-3).
You can also replace the WWW8Num1z* Character styles with None to avoid future problems, should you decide later to number your chapters.
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