The text book for Operating System by Galvin reads
"If there are n processes in the ready queue and the time quantum is q,
then each process gets 1/n of the CPU time in chunks of at most q time units.
**Each process must wait no longer than (n — 1) x q time units until its
next time quantum.** For example, with five processes and a time quantum of 20
milliseconds, each process will get up to 20 milliseconds every 100 milliseconds."

Is it correct? What happens if interrupt occurs while CPU is executing these processes. A process might have to wait for longer time then Or I am missing something obvious?