HSA Contributions Form 8889 confusion - double deduction?

I’m confused about reporting HSA contributions..
 
It’s my understanding that Box 1 on the W-2 is Wages earned minus contributions I made to my HSA that was pulled out from my paycheck
 
However, it seems you report those contributions on form 8889 as well.
 
This doesn’t make sense to me because that would be kind of like a “double deduction”:
 
1. one from the decreased wages that get reported on the W-2 and,
2. the other from the adjustments to income line on the 1040 that comes from Form 8889
 
Can someone clear this up for me? I have a feeling I’m not understanding Form 8889 properly.
 
Thanks.
 
Side note: If my understanding is correct about Box 1 on the W-2 being wages earned minus contributions I made to my HSA, do I reduce my wages by what my employer matches in HSA contributions as well?