SF Only: Muni Clipper Cards Charged Extra $4 on Some Vehicles Today

Heads up for anyone with a clipper card -- dbl-check your statement to make sure you didn't get over-billed. Was riding on muni earlier today and got charged $6 for a ride on the T -- normally a $2 ride. Flagged down a muni 'cop' and they told me "that's not right"...thanks sir...