26.2 & 13.1 Marathon

I came across 26.2 and 13.1 white sticker and black letters on many vehicles.

26.2 or 26.2 miles equates to 42.2. It's same or close enough to the official distance for a full marathon.
13.1 is just 1/2 of that or half-marathon.

I searched the web, the top two search results were car decals and temporary tattoos.