Poor for standard deductions

I like tax slayer, but the calculator is off-even on simple taxes.
I plugged in numbers into calculator app, then ran numbers on Form 1040 and Tax Slayer online. I have simple taxes-standard deductions-and calculator showed 3,000 higher refund than online or basic math. Im disappointed since I used calculator app a few weeks ago thinking I had great refund, then found out it was 3,000 lower when I did it "officially".

Basic filing about TaxSlayer: File your taxes