top命令的TIME/TIME+是指的进程所使用的CPU时间，不是进程启动到现在的时间，因此，如果一个进程使用的cpu很少，那即使这个进程已经存在N长时间，TIME/TIME+也是很小的数值。
此外，如果你的系统有多个CPU，或者是多核CPU的话，那么，进程占用多个cpu的时间是累加的。
top的manual page：http://linux.die.net/man/1/top
看看他的帮助说明：
l: TIME — CPU Time
Total CPU time the task has used since it started. When ‘Cumulative mode’ is On, each process is listed with the cpu time that it and its dead children has used. You toggle ‘Cumulative mode’ with ‘S’, which is a command-line option and an interactive command. See the ‘S’ interactive command for additional information regarding this mode.
m: TIME+ — CPU Time, hundredths
The same as ‘TIME’, but reflecting more granularity through hundredths of a second.