Hello, please posta screenshot of what you see at that link. From what I can see it shows (emphasis mine):
"We can construct queries to filter data based on various factors. To start, you specify how you want your data to be filtered using the orderBy parameter. Then, you combine orderBy with any of the other five parameters: limitToFirst, limitToLast,
startAt, endAt, and equalTo.
[...]
We can filter data in one of three ways:
by child key, by key, or by value. A query starts with one of these parameters, and then must be combined with one or more of the following parameters: startAt, endAt, limitToFirst, limitToLast, or equalTo."