Calibration:
By=-33 G-cm, Bx=+4 G-cm
-157 +64
-157 +62
-157 +65
Average: By=-157; Bx=+64

By=+33 G-cm, Bx=-4 G-cm
-93 +52
-92 +56
-91 +51
Average: By=-92; Bx=+53

By: (157-92)/2=+32 G-cm (Nominal 33)
Bx: (-64+53)/2=-5 G-cm  (Nominal -4)

Background:
By = (-157 - 92)/2 = -130 G-cm
Bx = ( 64 + 53)/2 = +57 G-cm