An Erlang is merely one hour of talk time, or 36CCS, or 3600 call seconds.
If you have two trunks and each of them carries 30 minutes worth of traffic in an hour, you had one Erlang of traffic that hour.
One trunk can not possibly carry greater than 1 Erlang of traffic, could that be the 0 and 1 thing you refer to?
Also, Grade of Service must be between 0 and 1. Either 0% of calls get blocked or almost 100% of calls get blocked.