There may be something in the design that has been omitted. Is there only one link? The occupancy of one link for one hour is 1 erlang. That would be 100% occupancy of that link.
Your traffic is given as just a bit over 1 erlang, indicating a percentage of 107% occupancy for the hour is the expected %.
This is also consistent with an estimate using the holding time. If holding time for the two outgoing calls averaged 31 minutes, this equates to about 103% occupancy (31+31=62) divided by 60 minutes per hour.
That does not leave any channel available for the incoming calls. And you might assume incoming and outging of same duration, there is a large possibility for error, given the small sample size.
The above occupancies are inconsistent with no failures and no overflows.
So – you have more than one channel? Use each channel with a possible occupancy of 1 for the hour, total available is the number of channels, your occupancy is 1.07 / number of channels.
Second possibility is incorrect label on the call holding time and this is not an average (unless you are speaking about a time period of several hours). In this case, you would assume the average occupany is 31 minutes per hour (outgoing and incoming) and the occupancy is 31/60, which is consistent with no failures or overflows.