I'm filing for my married friends and thought they should file jointly but the return is coming out better if I plug the numbers as MFS. Am I making a mistake?

[JoHarc]

They got married during October 2018, and lived separately with their parents until that point. I know one difference is that for MFJ, they obviously can't be claimed as dependents by their parents, but for MFS, I can select the option of "CAN be claimed as dependent but will NOT be claimed," even with MFS status.
MFS came back with about $1k greater total return than MFJ, which I was really surprised by, and the program doesn't come up with any errors during the last bit of analysis.
Am I missing something, or is this actually correct?

[Leonard]

No, you are not making a mistake in some cases a couple has a lower overall tax liability by filing separate than if they filed jointly.  If the program does not indicate any errors than it would appear that you have entered all the information correctly.