As I wrote, your G-code is using an offset:
N140 G00
G43 Z0.8000 H1 <- added spaces for readability
N140G00G43Z0.8000H1
Second, from your image it looks that you are using ball nose bit, not V bit as the code was generated for.
This are the comment lines at the beginning of your G-code:
( CHINESE NAME 650 20 deep )
( File created: Monday November 02 2020 - 08:21 AM)
( for Mach2/3 from Vectric )
( Material Size)
( X= 10.000, Y= 10.000, Z= 1.000)
()
(Toolpaths used in this file
(CHINESE NAME 650 20 deep)
(Tools used in this file: )
(1 = V-Bit {60 deg 0.625"})
Check in Mach 3 for Height offset for tool #1