Well, it doesn't necessarily mean anything. But it's still easy to guess what version number Android N will be.
You know how Google regularly teases (or sometimes trolls) the new version number of upcoming Android releases by placing the version in the clock in official screenshots? Well, doesn't have an official version number yet, and at those screenshots all have clocks pegged at 7:00.
The latest version of the Android N Developer Preview still has a "demo mode" that flips the clock to 6:00, so who knows. Is it a troll, or are we looking at the jump to Android 7.0?
The Android N Developer Preview is just that — a developer preview. It is not intended for daily use. That doesn't mean it's not cool, and that you shouldn't poke around. But know that things will break. Tread carefully. (And have fun!)