If the bot is idling or taking a break doesn't matter. If the session is running, you are still using hours. See breakhandlers as a feature if you are not at home or so. Always take breaks yourself if you are home and stop the bot in the meantime.
As Savior mentioned above, if you are using a bot which has "break handlers" (where it pauses the bot, your account is logged out and your character has a break from whatever skill/activity you were doing), this "paused" time is still included in your hours usage.