For example: the first word, Chapter, changes from a font size of 12 to about a font size of 80.
If you expect any answer, edit your question (don’t use an answer which is reserved for solutions) to provide minimal technical and “environmental” information: OS and LO version, structure of your document, how you typed it, your procedure used to print, …
Read these guidelines to improve your question.
Is the paper size shown in the printer dialog the same as the paper size in your document? If you have an A4 or Letter document and the printer is set to Label 73mm x 21 mm you will not get many words per page, and the preview will appear to show very large words.