Electric fence question

Does anyone know how to work out how much fence can be powered by an electric fence unit? 

We just bought one off the internet because it was a fraction of the price we'd pay locally, but it doesn't give us any info like 'powers 2 km of fence' or anything useful like that, only a list of figures about impulse rate, input voltage range, energy per impulse and current consumption, and I've no idea how to convert them into something I can get my head around.

check the manufactures web site for that model. much will depend on soil moisture and conductivity of the soil.

How long will your fence be?   How many strands?   What are you trying to keep in?  or out?

Is "energy per impulse" input or output?