If you use automatic paragraph numbering or bullets read Shauna Kelly's directions on numbering and bullets. Start with How to create numbered headings or outline numbering in Word 2007 and Word 2010. For large documents you must follow these directions or you will lose your hair!
(Mac version: Outline Numbering in Word for macOS - Best Practices - Brandwares). For styles attached this way, you also control the left indents through the Define New MultiLevel List dialog not the Ruler or the Modify Style dialog.

This may seem a bit convoluted at first, but it really is not. Just follow the steps. Shauna Kelly's instructions use the built-in heading styles, but you can use any existing paragraph styles including your custom styles. There are, however advantages to using the built-in heading styles when you create a Table of Contents. Here are some more advantages: Why Use Word's Built-In Heading Styles? by Shauna Kelly Note, you can modify these built-in styles to look exactly the way you want.
You want to do this even if what you want is a single-level list if you want the most control over your list.

Here is a link to a video by Deborah Savadra that tells how to set up a custom list style and multilevel list tied to existing paragraph styles.

• https://youtu.be/niD6VXPvAyU?t=487

The basic idea is that the numbering is set using the Define New List Style and Define MultiLevel List dialogs with each numbering level being attached to an existing paragraph style. Once you have this set up, you should not use the buttons for numbering in the Ribbon but rather apply the appropriate style for that level.

(Your multilevel list is not attached to any styles.)

You can save a document with this as a template for future documents if you want so you will not need to do this every time.

Styles in a multilevel list, when properly set up, can be a part of a [Quick] Style Set or applied by a macro using the Organizer method.

• [Quick] Style Sets and Word Themes in Microsoft Word
• [Quick] Style Sets
• A Global StyleSheet in Microsoft Word?

Here is the parallel article on bullets: How to control bullets in Ribbon Versions of Word by Shauna Kelly.

Word's numbering has worked this way since at least Word 97. Word Numbering Explained by John McGhie, MVP