Is it normal for my federal refund to differ when trying to file in turbotax and credit karma?

I'm trying to file my taxes but turbotax charges me for adding my 1098T and credit karma does not however my federal refund in turbo tax is much higher than what my federal refund for credit karma is. I was wondering if it's normal? Because if it is, then I would file with turbotax because it would only take $100 away and I would still have a bigger refund than what credit karma is telling me.