Look at this excerpt from a manual for SunFun Inc.

Which text element indicates that the text is in a sequence?

1. subheadings

2. bold words

3. numbering

4. bullets

Manuals usually show that they are in a sequence by numbering.

Explanation:

Numbering allows the information contained in a manual to be organized separately, showing "step-by-step" how a certain thing should be done. This allows to create a logical sequence showing the reader the steps that must be followed in a certain order, leading the reader to carry out an activity or reach the conclusion or the establishment of a final product in a practical, dynamic and efficient way.

Judging from other sources where the manual is shown:

numbering is the answer