The credit is per the individual who makes a retirement contribution. The maximum credit for each individual's retirement contributions is calculated on only the first $2,000 of that individual's retirement contributions for the year. If AGI limits the credit to 10%, the maximum credit per individual is 10% of $2,000 = $200, so it appears that the your credit calculated by TurboTax is correct.
Note that the IRS web page regarding this credit has erroneous information regarding the maximum possible credit and that might be misleading you into thinking that the credit is calculated differently. Chapter 3 of IRS Pub 590-A has the correct information: https://www.irs.gov/pub/irs-pdf/p590a.pdf
