It can be a slogan
for encouraging people when they are unhappy,
down or miserable.
Start From Zero was founded by a Hong Kong local street artist - Dom.
START stands for STreet ART, STencil ART and STicker ART.
The are two meanings of Start From Zero
He started performing street art from nothing, i.e. “zero; I hope that when someone see my stickers,
they will be like me, start doing street art from “zero”.
It can be a slogan for encouraging people when they are unhappy, down or miserable.
He also wants people to remind their friends of this slogan
when the same things happen.