TurboTax does these calculations correctly.  By law, on a joint tax return your eligibility to deduct a traditional IRA contribution or make a Roth IRA contribution is determined by your joint modified AGI.

My joint AGI is within the IRS limit, but when I add traditional IRA contribution, it shows message that the income limit (for one person) is more than the IRS limits and shows joint AGI as the number which is incorrect.

Make sure you entered the W2s and any other income  under the right person.  Or it might not be showing any income for that person.    

Yes....I had suspected the same and checked multiple times.. so still clueless why the software is showing these numbers