Carvel circle cutter jig sizing?

[Acrobat]

Hi, i have an issue understanding how one sets the circle hole cutting jig. I know it looks simple but I cannot get the correct size set. I set the tape readout to 60mm then placed it on the board with pin in the 4mm hole, drew the circle with a pen putiing the pen in the "v" of the jig. Measures 127mm, not 120!
Tried cutting the board out, I get a hole of 122 mm, and a circular piece out that measures 117mm, nowhere is it 120mm. What am i doing wrong?