Deductions & credits

Yes, if TurboTax shows that you owe more after you enter an IRA contribution, that means the program is showing an excess contribution. 

Since $600 is no where near an excess contribution by itself, I wonder if you have entered any other IRA contributions for the year. 

You are allowed to contribute up to $6500 total per year to all forms of IRAs ($7500 if you are over 50 years old). 

That means if you contribute $6500 to your Roth IRA and $600 to a traditional IRA, you have an excess contribution of $600. 

If you are making contributions to retirement plans through work, you only enter that information on the W-2 screen. 

To see if you have actually overcontributed, or just entered your information wrong, review the IRA contribution section:

1. Open your return.
2. Select Federal, then Deductions & Credits.
3. Scroll down to Traditional and Roth IRA Contributions, select Start or Edit.
4. Check the box next to the type of IRA accounts you have, then select Continue.
5. Answer Yes to Did you Contribute To a Traditional IRA?
6. Answer No to Is This a Repayment of a Retirement Distribution?
7. Enter your traditional IRA contribution here. As the note here says, don't include Roth contributions, rollovers, or any amount already shown on your W-2 form. Select Continue.
8. Answer the next few screen according to your situation. 
9. Repeat the process for your Roth IRA if you have one. 
10. The program will tell you if an excess contribution was detected and will provide some guidance on how to fix it. 

If you have overcontributed to your IRA accounts, you can contact your IRA administrator and take a corrective action, such as removing the excess contribution plus earnings from your IRA. 

As long as you make any needed corrections by April 15, there is no penalty.