Trying to see just how bad I did for one of my com classes.

In the grade report it says I got a C- and when looking at the 'grade conversion table' I found on this site:

http://studentsuccess.mcmast er.ca/...ion-chart.html

It shows me several different grades for C-. Beside the C- on my grade report is a '4' so I figured I look under the 4 on the chart where the it meets the C- which is a 60-61.

Is this the correct way to convert the C- into a numerical value?

The percentage column that Mcmaster uses is the 3rd. So because you got a 4 that means your grade fell somewhere between a 60 and a 62. A 5 corresponds to 63-66, a 6 to 67-69 and so on.

The grade conversion system you found is for converting between different scales used at different schools. The one you're looking for is in the course calendar and numerous other places on the McMaster website: https://iss.mcmaster.ca/incoming-exc...ng-system.html
Or, it is column 3 on the chart that you found. The "4" is not telling you what column to look under, it is telling you what your grade is on the 12-point scale. The columns refer to different schools, as indicated underneath the chart.