[breller]

A coworker quizzed me on a diazepam. He asked be if I could draw the structure. After some head scratching I finally turned to the internet. I've been out of college for over 10 years now and specialize in inorganic chemistry so I've lost most of my organic chemistry knowledge.
The compound in question is, 7-chloro-1-methyl-5-phenyl-3H-1,4-diazpin-2-one.
Here's the part that is stumping me. After drawing the structure and determining I had it correct via various websites, I cannot for the life of me figure out how that can be 7-chloro? I've counted from everywhere and can't get a 7. I've even started with the chloro and counted backwards and it still doesn't work out.
Based on the name and structure I can see where 1 is and the phenyl, the methyl, the =O and the location of the N's at 1 & 4 all make sense. The only one that doesn't make sense, if you start counting from the 1 position, is the chloro.
This isn't any big deal, I don't need this answer for a test or homework or anything, it's just confounding me!!

Thanks.

[AWK]

Numbering is from nitrogen bearing methyl group clockwise (structure in wikipedia) with omission of joint of rings (finally joint of rings - carbon atoms of joint, if numbers are needed, are numbered as 5a and 9a , respectively).

[breller]

Thanks AWK.
That makes a lot more sense.
Hopefully I'll get some sleep tonight! 

[AWK]

Check numbering carbon atom in tetradecahydroanthracene.

[Vidya]

Good question and well answered by AWK
check the attached image

[AWK]

... and other four?

[Vidya]

... and other four?

check this image ...

[AWK]

OK