Translation:I am leaving the convenience store.
There are a few semi-comprehensive discussions on this thread, look for posts by IsolaCiao: https://forum.duolingo.com/comment/38580697
Also here's a moderator comment: https://forum.duolingo.com/comment/27657664?comment_id=27665614
In brief summary "を出ます" is sort of an idiomatic expression, which is why を is used despite the fact that "出る" is intransitive. And "will leave" is probably a more accurate translation, but to quote the mod
"...English present progressive is often used for future actions, which falls under the non-past Japanese umbrella:
- 父と食べます = I eat with my dad.
- 父と食べています = I am eating with my dad (right now).
- 父と食べます = I am eating with my dad (later today).
You're mixing up simple present and present continuous tenses. You might not say "I leave the store" (unless describing a habit, like "I eat breakfast every day") but you might say something like "I am leaving the store" when on the phone with someone and describing what you're doing in that moment. I am not sure that Japanese makes a distinction between present simple and present continuous, but apparently コンビニを出ます can be translated to both "I leave the convenience store" (simple) and "I am leaving the convenience store" (continuous).
There are lots of convenience stores around train stations in Japan. When we were out and about in Tokyo, often times one of us would nip into one to buy a drink or snack. Of course there would be a queue... and somebody rings you in a panic because there's a chance we could miss the train: "I'm leaving the convenience store" you yell back as you start running, clutching onto your drink and bento box!
Maybe because it's describing a future action that will happen immediately, it uses the て form in Japanese? Unless it's a long drawn out process for some reason. In English you would almost surely use the progressive form though, unless describing a pattern (present) or a future action. Hopefully someone else can clarify.