How does one go about actually repaying the Help To Buy back to Revenue?

Revenue require you to live in a house for 5 years, or else they can claw back the HTB.

But I can't find info on how exactly they claw this back and how they expect the funds to be repaid.

If I don't have 30k sitting in the bank, how do they expect to be repaid? Can this be done over the course of years? Or are they expecting it all up front? It's not clear from the HTB documentation.