What is Vocabulary Knowledge Scale? How does it work? Is this method reliable? – graduate researcher

What is Vocabulary Knowledge Scale? How does it work? Is this method reliable?
https://www.utpjournals.press/doi/abs/10.3138/cmlr.53.1.13
https://books.google.com/books?hl=en&lr=&id=_g0eSfesA-0C&oi=fnd&pg=PA174&dq=vocabulary+knowledge+scale+1993&ots=Bgl-Jy4_oS&sig=RPdlIrhyDb6tKcBoAHm5giPQtcs#v=onepage&q=vocabulary%20knowledge%20scale%201993&f=false