Step-by-step explanation:
Amy Tan acknowledges about the lack of knowledge she has about the English language. She is stating that she is only speaking from her own perspective i.e., her own understanding of the English language.
She has no knowledge of how people in other countries speak in English. The statement indicates what we should expect from the rest of her speech.
English is the most popular language on the Earth. However, as it is spoken by people from other countries the native language influences English. Amy Tan does not know how much this affects the English language.