Why does Turbotax want to tax my HSA contributions?

Ive entered the amount in box 12 code W into Turbotax and this immediately causes my tax bill to increase.  Ive always been under the impression HSA funds are tax free so I dont understand why this happens.

 

Of course its possible that Im completely misunderstanding that, but if someone can let me know that would be greatly appreciated.

 

Thanks much for any information!