That might happen if you're using the auto conversion feature - it's turned ON:
The app will convert to your customers local currency - wherever they are from.
That means, that the local currency will be added to the list, for that specific customer in that specific session.
If you want to avoid it, toggle this checkbox:
^ Auto convert to these currencies only
In case you do, a visitor from a non supported country will fallback to your store default currency.