Tune with high N2 content but low O2 content

How can I have high Nitrogen content in my tune but low O2 content? 

I have an 7890B GC with 5977B and also 7697A Headspace. 

We also have a Helium conservation module. 

It doesn't make sense. If it's a leak, I must have the same ratio (4:1) For N2 over O2. 

Anyone have seen that ? 

Is it possible that the helium conservation module valve leak as let Nitrogen mix with Helium ?  

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