It would run at 10:00:00 as it is in the window you have specified.
Cron 0 0 8-10 * * *:
8:00:00
9:00:00
10:00:00
Cron 0 0 8-9 * * *:
8:00:00
9:00:00
To specify minutes you can do the following:
Cron 0 */5 8-10 * * *:
8:00:00
8:05:00
8:10:00
...
9:00:00
9:05:00
9:10:00
...
10:00:00
10:05:00
10:10:00
...
10:55:00