An E1 consists of 24 channels. You may easily look up from an Erlang-B table for the traffic corresponding to a 24 channels with 1% blocking. The figure is 15.3 Erl. It means that an E1 can support a traffic of 15.3 Erl with a tolerance of 1% being blocked.
It appears (I’m not quite certain) that 0.153 Erl traffic would be blocked. The “carry traffic” should then be 15.147 erl [15.3 less 0.153].
In your case, the capacity of the bottleneck should be of concern. And the bottleneck may not (actually, not likely to be) the E1.