Spridget Speedo Marks

Anybody out there know what means the short line
on the Speedo face that comes just BEFORE the heavy
line at 0 mph? It's just below the retractable pin on which
the needle rests when you ain't moving. (Izzat that only
special Spridgets can go -5 mph?)

Oh Yass, also what is that retractable pin used for? Might
this be used when zero(e)ing the needle?

Enquiring Minds want to know.

chuckC