If I am correct, this is showing a 4 channel site, because there are 2 voice slots per frequency.
So frequency 1 is voice slots 1 and 2, frequency 2 is voice slots 2 and 3, and so on.
A trick that I use, (if you have a second computer available), is to watch the control channel on one computer to monitor activity, and use the second to find and follow the voice frequency. On the systems where I live, the CC seems to prefer the frequency that has voice slots 1 and 2 when idle, but it does move around somewhat when there is voice activity, and then returns to the frequency with voice slots 1 and 2.
I don't know if this is the same for your system, perhaps someone else can shed some light on this.
Mike