Hi Nick,
You will need to resolve value of parameters that share the same name when you run the job if they have different values. Take this example for instance:
I have two "clientName" parameters with two different values (default values). In this case, I would need to specify which value "clientName" should resolve to once I run the job.
In the run job dialog, you will find a "Variables" section near the bottom which lets you specify what value the "clientName" parameter should resolve to (this can also be done if you are running the job via the API):
Alternatively, you can specify an override in the "Manage parameters" dialog which effectively does the same thing:
Edit: Fixed screenshots!