Load the default mission and open up DefaultSC. Set the Cartesian state to:
Hit apply and change the state type to Keplerian. There is an error in the SMA. The expected SMA = 42095
But the value GMAT outputs SMA = 42095.00001108487.
This leaves an error of 0.00001108487 which is outside the error tolerance of 1e-5.
Then change the state type to Modified Keplerian. There is an error in RadApo. The expected RadApo = 76536.3628709998
But the value GMAT outputs RadApo = 76536.3628869933
This leave an error of 0.000015993500710465014 which is outside the error tolerance of 1e-5.
Finally change the state type to Equinoctial. There is an error in the SMA that is the same as the Keplerian state type error.