You pulled a double shift.
kinda.
we yhave an eight hour guarantee at my job.
if i were to pick up a job at the dispatch hall and the job finishes (ie: no more cargo to handle and the ship sets ready for sail) then we are released with eight hours of pay.
say for example:
the other day i picked up a job that was a dead shorty. we finished in two and a half hours. i am free to go back to the dispatch hall and pick up another job that is hanging (left unfullfilled, a replacement was called, an elevation replacement, etc...) and i will get paid twice (16 hours) in an eight hour block of time.
that is a double up.
pulling a double shift would be called doubling back.
for example:
i am nights. i can work my shift (6pm- 3am) and then i can go back to the dispatch hall for the first shift dispatch (days 8am-5pm). and i can work up to 14 shifts per week that way. or, unlimited overtime. but, that could be exhausting for a man of my years, and besides, after a certain point it all goes to uncle sam.