Web of Science includes not only the Citation information but also Cited By information.
It looks at who the author included in the bibliography (citation information) and connects to literature that is now connecting back to this article (cited by information).
If the information is not fully avaialble (e.g. no title), you may need to look at the reference list (bibliography) of the article.
Google Scholar includes Cited By information. The numbers between Web of Science and Google Scholar regularly do not match. Web of Science is usually more restrictive in what it will include in Cited By counts.