I have a 2001 $1 star note that starts off with f06700xxx. When I looked it up the reference page shows the following"
Run Size 3,200,000
Total Printed 7,360,000
Other Info

Run Number 3

Run Range: 06400001 #8596; 09600000

Printed in Fort Worth, TX in May 2004

No Gaps
My not appears to be early in the run history but by the s/n's shown there is no way that they printed 7.4 million of these things.
Is this some sort of new math?