Are you certain they are in BoP custody? BoP is federal (not state or county).
Inmate Intake
digitalpoint
Martha carefully picked the day she started her incarceration, leveraging technicalities, and got out 4 days early.
Lori left it to chance and ended up spending an extra 3 days in prison. If she had reported to prison 1 day earlier (Oct 29), she would have gotten out 4 days earlier (Dec 24), and been home for Christmas.
If you are facing sentencing, be smart... Figure out the best day to report to prison.