It would be the total costs. It's due to inflation, because it's a program that's going to take 25 or 30 years. If there's a one-year delay, then overall spending is deferred and inflation has a compounding effect on the duration of the program. As a result, total costs would be $2.3 billion more for a single year of delay.
On March 8th, 2021. See this statement in context.