Trimble JXL file

Hi, I have found something I don't understand in these files.
A point record has a face 1 and face 2 record, then a MTA (mean turned angle) record.

The horizontal circle in the MTA record does not appear to be the average of the two (after converting face 2 to face 1) as you might expect.

I'm sure there is a simple explanation?

		<PointRecord ID="00000454" TimeStamp="2015-11-18T16:11:15">
<Name>R15</Name>
<Code>RETRO</Code>
<Method>DirectReading</Method>
<SurveyMethod>Fix</SurveyMethod>
<Classification>Normal</Classification>
<Deleted>false</Deleted>
 
 
 
 
<Circle>
<HorizontalCircle>36.2379699</HorizontalCircle>
<VerticalCircle>86.026194</VerticalCircle>
<EDMDistance>44.72911</EDMDistance>
<Face>Face1</Face>
<HorizontalCircleStandardError>0.00027777777778</HorizontalCircleStandardError>
<VerticalCircleStandardError>0.00027777777778</VerticalCircleStandardError>
<EDMDistanceStandardError>0.00208945822</EDMDistanceStandardError>
<EDMMeasurementMode>Fine</EDMMeasurementMode>
</Circle>
<StationID>000003d7</StationID>
<BackBearingID>000003d8</BackBearingID>
<TargetID>000003e4</TargetID>
<Pressure>986.5</Pressure>
<Temperature>20</Temperature>
 
 
 
 
<ComputedGrid>
<North>15856.297373964</North>
<East>93305.628052364</East>
<Elevation>110.61595261071</Elevation>
</ComputedGrid>
</PointRecord>
 
 
 
 
<PointRecord ID="00000458" TimeStamp="2015-11-18T16:11:23">
<Name>R15</Name>
<Code>RETRO</Code>
<Method>DirectReading</Method>
<SurveyMethod>Fix</SurveyMethod>
<Classification>Normal</Classification>
<Deleted>false</Deleted>
 
 
 
 
<Circle>
<HorizontalCircle>216.2377053</HorizontalCircle>
<VerticalCircle>273.9737808</VerticalCircle>
<EDMDistance>44.72942</EDMDistance>
<Face>Face2</Face>
<HorizontalCircleStandardError>0.00027777777778</HorizontalCircleStandardError>
<VerticalCircleStandardError>0.00027777777778</VerticalCircleStandardError>
<EDMDistanceStandardError>0.00208945884</EDMDistanceStandardError>
<EDMMeasurementMode>Fine</EDMMeasurementMode>
</Circle>
<StationID>000003d7</StationID>
<BackBearingID>000003d8</BackBearingID>
<TargetID>000003e4</TargetID>
<Pressure>986.5</Pressure>
<Temperature>20</Temperature>
 
 
 
 
<ComputedGrid>
<North>15856.297473007</North>
<East>93305.628442692</East>
<Elevation>110.61595446999</Elevation>
</ComputedGrid>
</PointRecord>
 
 
 
 
<PointRecord ID="0000045c" TimeStamp="2015-11-18T16:11:23">
<Name>R15</Name>
<Code>RETRO</Code>
<Method>MeanTurnedAngle</Method>
<SurveyMethod>Fix</SurveyMethod>
<Classification>MTA</Classification>
<Deleted>false</Deleted>
 
 
 
 
<MTA>
<HorizontalCircle>334.36614204846</HorizontalCircle>
<VerticalCircle>86.0262066</VerticalCircle>
<EDMDistance>44.729265</EDMDistance>
<HorizontalCircleStandardError/>
<VerticalCircleStandardError/>
<EDMDistanceStandardError/>
<NumberOfHorizontalAngles>2</NumberOfHorizontalAngles>
<NumberOfVerticalAngles>2</NumberOfVerticalAngles>
<NumberOfDistances>2</NumberOfDistances>
</MTA>
<StationID>000003d7</StationID>
<BackBearingID>000003d8</BackBearingID>
<TargetID>000003e4</TargetID>
<Pressure>986.5</Pressure>
<Temperature>20</Temperature>
 
 
 
 
<ComputedGrid>
<North>15856.297423487</North>
<East>93305.62824753</East>
<Elevation>110.61595354038</Elevation>
</ComputedGrid>
</PointRecord>