My wife & I are using Turbotax Home & Bus. for taxes.When I add my wife's SEP ira contribution (~8k) the tax reduces by $60.Is it a glitch?Solo401k ($8k cont.) saves ~2k

My wife receives 1099NEC and I am on W2. We are trying to maximize IRA/401k contributions. We do not have any employer 401k or IRA. We have our own HSA and IRA accounts. We are looking into opening a SEP IRA or a Solo 401k for her. Adding $8000 to SEP IRA (20% of her income) reduces the taxes by $60 but adding the same to a solo 401k instead saves about $2000. Is this a software glitch? Any suggestions on what could be the issue?