It appears your footnote numbering has been corrupted, rather than there being a custom setup. Fixing it is fairly simple, though:
1. Convert all footnotes to endnotes (I don't know the Mac Ribbon/Menu structure for this).
2. Run the macro in
https://www.msofficeforums.com/word-...html#post47377
3. Convert all endnotes to footnotes.
For Mac macro installation & usage instructions, see:
https://wordmvp.com/Mac/InstallMacro.html