Duo doesn't always give us a complete sentence, so there's no reason to assume this would be one. Am I correct in thinking this is like the implied "you" in English? For example: "(You) walk during your lunch hour." One wouldn't say "(You are) walking during your lunch hour", because it's more of a command or suggestion to "you".
Since "heure de déjeuner" is singular, the use of "votre" matches the singular thing referred to. One would not mix the polite verb form (marchez) with the familiar "ton". It's all explained here: http://french.about.com/od/grammar/a/adjectives_possessive.htm