See attached script (received from DJC unit tests) that first simulates and then solves for an overall thrust scale factor.
The script sets the initial estimate for the solve-for as follows:
Thruster1_SetPoint1_Est.ThrustScaleFactor = 0.96
Run the attached script - you can stop the run after the initial iteration. I would expect that the a priori state would reflect this value of 0.96 but it does not as shown below:
Perhaps, GMAT is just reporting a "Delta" from the estimate. If so, this should be an easy reporting fix.
Build used is GMAT-R2015a-TSF_Solve_For_Build-x86.zip delivered 9/22/2016.