Apskip, your system still makes no sense, because if you refer to the two hour premiere episode as just "Episode 1", you wouldn't call this "Leg/Episode 6", but would actually call it "Episode 5." There's no good reasoning I know of for calling it "Leg 7". The actual leg number is 6.
1. Episode 1/Legs 1 and 2
2. Episode 2/Leg 3
3. Episode 3/Leg 4
4. Episode 4/Leg 5
5. Episode 5/Leg 6 - tonight's episode.