Eight hours after Apple (AAPL) CEO Tim Cook pronounced himself “very thrilled” with what he described as “record weekend” sales of the third-generation iPad, the company issued a press release clarifying what record the new iPad had broken.

It wasn’t Apple’s all-time best hardware launch. That record is still held by the iPhone 4S, which sold 4 million units in 3 days.

It took the new iPad nearly 4 days to sell 3 million units, according to the press release Apple issued at 5 p.m. Monday.

It quotes Phil Schiller, Apple’s marketing chief, declaring that “The new iPad is a blockbuster.”

It’s hard to do comparisons, because the new iPad launched in more countries than the iPad 2 and was available for pre-order a week ahead of time.

Also, we don’t actually know how many iPad 2 units sold the first weekend because Apple never issued a Monday-after press release. Supplies of the iPad were constrained at this time last year, and the sales number Apple finally released in its Q2 2011 earnings report — 4.7 million iPads — was considered a disappointment.

At 3 million units, it’s hard to cast the new iPad as disappointment, no matter how hard some will try.