Question about how deductibles work?

I have a surgery I want to schedule that I have to go through an out of network provider to get. My insurance has deemed this surgery medically necessary so they will process it at my out of network level with a 700 dollar deductible.
I am wondering if the surgery is 13,000 how much I will end up paying out of pocket. They said Once the deductible has been met the plan will pay 60% of the allowable amount. The allowable amount can differ from what we charge; an example would be if the bill is $100 and they allow $80 they pay 60% of the allowable and the difference is patient responsibility. So what does that mean? Will I just not know what I’m paying until I schedule it??? Or after?