It generates numbered links. If your H2/H3 text already includes a number, then it appears twice.
The table of contents generates links with text retrieved from the headings, so if the headings contain numbers, they will also appear in the TOC links – this is normal behavior.
It does not handle a missing level very elegantly, in my case it included extra, blank entries in the TOC due to a missing level (My text was going straight from H2 to H4 in some cases by design)
The outline level of the headings is incorrect, and the TOC based on that, displays empty items because it lacks the correct outline. Instead of using H4, use H3 heading with .h4 class:
<h2>1. Dominant ecommerce platforms</h2>
<h3 class="h4">Salesforce B2C Commerce</h3>
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