Danb,

Speaking of Caesar coordinates,
In our case radial is represented by +Z and hence the thumb faces along +X
It is known that CAESAR II uses the "right hand rule" to determine positive/negative rotation.
Hence the nozzle rotation which is downwards will yield a Rx=+1.21 deg (In this specific case, not necessarily always!).

If the same nozzle had been facing along -Z, the rotation to be fed in Caesar would be Rx=-1.21 deg.

I presume your are taking to image what I have attached below, This image shows the axis orientation and presuming API also uses a "right hand rule" to determine positive/negative rotation it would match with our second case (i.e,) Nozzle is oriented along -Z and will yield a Rx=-1.21 deg.

Coordinate matching can always be done, it would be generally missed by a stress analyst thinking the error report shows rotation w.r.t Nozzle axis modeled in Caesar, and this was the concern.