Hi Rich!
It is very simple:)
If you have a channel with 64 kbit/s (230400 kbit/h)throughput and your information source bitrate is 230400 kbit/h, then you can say that your source is creating load with 1 Erl intensity on that channel. Accordingly – 230400/2 = 0.5 Erl, 230400/4=0.25 Erl for this case.