You really should refer to it as off of TDC, because deck heights can be different on different blocks or piston combo's so measuring a pistons depth 'in the hole' can be misleading. Going off TDC will eliminate any error for block or piston differences. You could use a degree wheel or there are charts that translate degrees into inches before TDC, all you need to know then is the fire point or position of the flywheel in relation to the coil when it's gonna fire. When the right edge of the magnet reaches the outer edge of the right coil leg , that's where it fires so you put the crank at the timing you want, for example a stocker that you want at 29 degrees is right at .195 before TDC, with the crank held at that point you line up the fire marks I mentioned above and torque the flywheel on. Re check after torqueing to see if it moved on you any. Jon