$V_{\epsilon}(x^*)$ notation

Question

What does the following notation $V_{\epsilon}(x^*)$ in the context

and there are infinitely many terms of $a_n$ in $V_{\epsilon}(x^*)$

on this link.

Answer 1

From the context it looks like the interval $$ V_{\epsilon}(x)=(x-\epsilon,x+\epsilon)\ . $$