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TeX Frequently Asked Questions
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LaTeX constructs the table of contents, list of figures, tables, and similar tables, on the basis of a layout specified in the class. As a result, they do not react to the sizes of things in them, as they would if a tabular environment (or something similar) was used.

This arrangement can provoke problems, most commonly with deep section nesting or very large page numbers: the numbers in question just don’t fit in the space allowed for them in the class.

A separate answer discusses re-designing the tables and those techniques can be employed to make the numbers fit.