Agilent Technologies N9913A User Manual page 138

The yellow data trace displays the current measurement with trace math applied.
The math operation symbol [D/M] is displayed on the lower left corner of the
screen. Learn more about Trace Math on page 187.
NOTE Data interpolation is NOT supported. If the Resolution setting is changed with
Trace Math enabled, the FieldFox will disable the math operation.
138 FieldFox User's Guide