Modifying g-code

I am using Fusion360 to generate g-code for aluminum milling, then sending the g-code to easel and carving with a .25" end mill. In general, it is working great!
Today, I ran a file that took 5 hours to cut in aluminum, however, it did not cut all the way through my material. It is so close! If it had done a few more passes at the very end of the job, the aluminum part would be free.

Does anyone know if I can use the g-code generated in Fusion360 and just run the last part of my job again a little deeper this time? Without running the entire 5 hours again? I kept my machine at zero, so I will be able to find it again.

It is a single cut that goes slowly to the bottom.

Find the last pass which the machine made — delete everything else in the file except for the header/setup information at the top, save under a new name — information about G-code here: http://www.shapeoko.com/wiki/index.php/G-Code

Adjust your Z-axis zero down by the depth you would like to cut

Send the new file.

Thank you so much! That worked.