There are a number of reasons why a chart may show extra bullet points beyond the number wanted, but the most salient reason is that the return or enter key was pressed after the last bullet point, which created a new bullet point with no text.
If a new bullet point with no text was created after the end of a bulleted chart, the simplest way to remove those bullet points is to recreate the chart. When recreating the chart, enter the original number of bullets, but at the end of the bulleted list, do not press enter. If you must press enter, press the delete key, which will then delete the newly created extra bullet point, thereby eliminating any issues with extra bullets in the chart. Creating bulleted lists in charts creates a number of options.
There are a number of types of bulleted lists, including lists that include bullet points, numbers, stars, or some other combination of symbols that represent bullet points. Another aspect of bullet lists is the tiers that are created by pressing the tab key. Tab can change the type of bullet that is used and results in a variety of nuanced list types that can be interpreted in various ways.