A family of Microsoft word processing software products for creating web, email, and print documents.
The best practice is to create outline numbered styles, which can then be applied reliably. Here's an article about creating such styles in Word for Mac. This article is focused on numbered heading styles: Outline Numbering in Word for OS X - Best Practices
But your text sounds like you're applying numbering to text instead of headings. In that scenario, this article explains how to apply outline numbering to any styles: Outline Numbering Variations - Best Practices
After creating these styles, apply them to text that needs to be numbered. After a break in numbering, reapply the style where numbering has to resume. In most cases, that's all you have to do: Word picks up the previous number for that style and increments it.
If Word doesn't get it right the first time, right-click on the incorrect number and set it to Restart Numbering or Continue Numbering.