It is a set amount, approved by Parliament. If the debates commissioner were to run into a wall—and they've given no indication—there would be a process as with any department, whereby the debates commissioner would put in a funding request to the minister and it would go from there. Again, there has been no indication that they feel they don't have enough money, but if they did, there are mechanisms.
On February 19th, 2019. See this statement in context.