When indents change unexpectedly like that, it is a sign that they weren't specified properly from the start. For numbered lists, you have to set the indentation around numbers in the Adjust List Indents dialog box (for single-level lists) or in the multilevel list dialog box (for multilevel lists). See
Number Alignment (Ribbon). However, as Charles said, a long-term solution would be to set up numbering properly with styles; have a look at
How to create numbered headings or outline numbering in Word 2007 and Word 2010 | ShaunaKelly.com.