Electrical Symbols

what is this electrical symbol? zero with a line through it?

my electrician wired the home. on a light switch wire he wrote a “zer 0; with a line through it’

what does this mean??
obviously a Number zero… I didnt say letter.

anyone know what this NUMBER zero with a line through it means???
yes.. i am an engineer also.
its written on a yellow 12-2 switch for some recessed cans or some pendant lighting

For a true answer just ask the electrician that wired the home.

Electronic Symbols & Wiring Diagrams 1