Formula for SS7 link for GSM

Could help somebody. I need information about SS7 link.
How is right to calculate traffic on SS7 link in GSM.I need to know traffic on each SS7 link between MSC and BSC.

link load(Erl) = [(A+ B * 6)* 8Bits] / [64kbit/s]
A= SIO and SIF numbers per second
B=MSU number

Is it right?

According to ITU-Q702,704,706 protocols, SS7 RSL bears 0.2ERL in signal pass; for the consideration of link backup, the ceiling cannot exceed 0.4ERL.